feat: support mixed runtime and metadata execution

TODO.md

@@ -58,8 +58,8 @@ checked immutable-array/slice views, by-value iteration and erased arguments;
 mutable metadata borrowing remains open.
 ordinary metadata-input procedures also compute owned runtime values, including
 reflected field names/counts, recursive helpers and fallible cleanup.
-explicit and inferred local metadata storage also make ordinary procedures
-constant-input producers, preserving owned updates, loops, recursion and cleanup.
+explicit and inferred local metadata storage also coexist with ordinary runtime
+parameters and effects; parameter-dependent metadata retains constant-input execution.
 `field!` selects record/tuple/enum and sequence members using compile-time names,
 including runtime places and type-control updates without runtime reflection.
 `struct_type!` generates ordinary/C-layout records from constant name/type/default
@@ -71,7 +71,7 @@ with static tags and exact by-value payloads, preserving runtime dispatch and sc
 `typeinfo!` exposes owned compile-time array/distinct/record/enum metadata, including
 readonly field collections, exact nominal types and reflected generated storage/defaults.
 the existing `meta.EnumFieldStruct` and `enummap.EnumMap`, `init` and `get` work;
-general type-valued execution, broader materialization and full library acceptance remain open.
+mutable metadata borrowing, broader materialization and full library acceptance remain open.
 `some!` preserves nested optional presence; ordinary procedures initialize concrete
 runtime `undefined` locals and compute fully initialized materializable constants.
 the existing `ArrayList` uses nested generic inference, file-local helpers and
@@ -180,10 +180,11 @@ test discovery and FFI remain outside these completed slices.
   - [x] readonly type-slice checkpoint: `[]type` and slices of type-valued records/arrays use owned compile-time snapshots. contextual literals, immutable readonly array views, nested slice views, checked `usize` bounds/indexing, `.len`, empty shapes and ordinary/inline by-value iteration preserve exact nominal leaves. constant-input procedure parameters/results, erased generic inputs, optional/fallible nesting and normalized cache keys generate runtime storage/defaults through interpreter/native execution. mutable annotations/backing, metadata sentinels, invalid ranges/indices, readonly writes, incomplete leaves and runtime dependencies retain diagnostics. imported private types, source/session disposal, shared construction bounds and repeat compilation preserve ownership. mutable metadata borrowing, runtime metadata storage, general type-valued execution and broader constant materialization remain open.
   - [x] tagged type-storage checkpoint: tagged unions containing type leaves own active payload snapshots through typed/contextual construction, direct and nested field/index updates, immutable by-value matches and whole-value variant replacement. constant-input procedure arguments/results, erased generic inputs and normalized cache keys preserve nominal leaves and saved copies while generating runtime storage/defaults through interpreter/native execution. undefined union locals and nested record/array storage require whole-value initialization; inactive reads/writes, malformed explicit tags, nominal initializer conflicts, readonly updates, incomplete results and narrow overflow retain diagnostics. explicit sparse tag enums may contain unused members without adding match cases. imported private types, source/session disposal and repeat compilation preserve ownership. untagged metadata layouts remain invalid; mutable metadata borrowing, runtime metadata storage, general type-valued execution and broader constant materialization remain open.
   - [x] metadata-input execution checkpoint: procedures with ordinary type-valued parameters execute entirely at compile time even when returning runtime-representable values. all inputs remain explicit constants; owned scalar/record/array/string results, recursive readonly metadata iteration, reflected field names/counts and private nominal leaves work through interpreter/native execution. plain/fallible `void` retain bare-return/fallthrough semantics; ordinary fallible results propagate through `try`/`catch` and run scoped `defer`/`errdefer`. runtime dependencies and incomplete payloads retain diagnostics; source/session disposal and repeat compilation preserve ownership. dependent signature parameters still require `$`; general type-valued execution, mutable metadata borrowing and broader constant materialization remain open.
-  - [x] explicit metadata-local execution checkpoint: procedures with explicitly annotated type-valued locals execute entirely at compile time without metadata inputs or results. scalar inputs remain explicit constants; nested metadata records/arrays, undefined initialization, owned copies, checked field/index updates, loops, captures, recursion and scoped fallible cleanup reuse existing type-control execution through interpreter/native paths. runtime inputs and uninitialized leaves diagnose; ordinary unannotated local type aliases retain runtime parameters. imported private nominal leaves, source/session disposal and repeat compilation preserve ownership. inferred metadata-only locals are covered below; mixed runtime/type-valued execution, mutable metadata borrowing and broader constant materialization remain open.
-  - [x] inferred metadata-local execution checkpoint: inferred mutable type bindings and metadata array/record/tuple locals select fully constant-input execution without metadata inputs, results or local annotations. literal/helper results, checked field/index/optional projections, yielding blocks and conditional/fallible selection preserve owned copies, nominal leaves, whole-value replacement, loops, recursion and scoped cleanup through interpreter/native execution. inferred array elements remain readonly; runtime inputs diagnose. ordinary local aliases and scalar metadata projections retain runtime parameters. ordinary fallible success/error snapshots use checked channel discrimination rather than assuming every payload carries a nominal type. imported private types, source/session disposal and repeat compilation preserve ownership. erased compile-time-only procedures cannot become runtime entries. mixed runtime/type-valued execution, mutable metadata borrowing and broader materialization remain open.
+  - [x] explicit metadata-local execution checkpoint: procedures with explicitly annotated type-valued locals support constant-input execution without metadata inputs or results. nested metadata records/arrays, undefined initialization, owned copies, checked field/index updates, loops, captures, recursion and scoped fallible cleanup reuse type-control execution through interpreter/native paths. uninitialized leaves and runtime dependencies diagnose; imported private nominal leaves, source/session disposal and repeat compilation preserve ownership. independent runtime parameters are supported by the mixed-execution checkpoint below.
+  - [x] inferred metadata-local execution checkpoint: inferred mutable type bindings and metadata array/record/tuple locals support constant-input execution without metadata inputs, results or local annotations. literal/helper results, checked field/index/optional projections, yielding blocks and conditional/fallible selection preserve owned copies, nominal leaves, whole-value replacement, loops, recursion and scoped cleanup through interpreter/native execution. inferred array elements remain readonly; ordinary local aliases and scalar metadata projections retain runtime parameters. ordinary fallible success/error snapshots use checked channel discrimination rather than assuming every payload carries a nominal type. imported private types, source/session disposal and repeat compilation preserve ownership. independent runtime parameters and metadata-local entry points are supported below.
   - [x] formatted-IO acceptance checkpoint: existing `std/io.print` parses constant formats and expands tuple fields through interpreter/native execution without replacement or adapted library code. escaped braces, all integer bases/boundaries, booleans, strings/arrays, sparse/aliased enums, nested scalar distinct values, runtime arguments and computed formats retain exact output; short writes, zero progress, invalid callback counts and write errors retain checked propagation. malformed formats, wrong tuple/count/type inputs and unsupported specifiers diagnose. native `f64` default/decimal/scientific formatting uses imported variadic `snprintf` at `-O0`/`-O2`, while interpreter FFI remains a demanded trap. character literals preserve Unicode code points and byte escapes; newline-separated conditional branches and package-local visibility match Bro. partial compile-time prefixes infer remaining arguments without overriding explicit values; pure type builtins and effect-free bound type helpers specialize guards. `rem!` preserves exact numeric types, signed-minimum remainder and checked zero divisors. immutable C byte-pointer coercions, borrowed pointer-to-array slices and optional presence retain mutability/nominal checks. inline iterables propagate constant demand through original parser calls, metadata indexing and borrowed initialization; guarded errors follow reached control flow, owned snapshots commit local mutation, contextual constant numeric locals preserve rigid boundaries, and runtime bodies/effects remain runtime. general type-valued execution, broader materialization and broader `meta` acceptance remain open.
-  - [ ] remaining gate: general type-valued compile-time execution, broader constant materialization (including address-bearing untagged unions, nonnull data pointers and mutable slices), plus remaining existing-library acceptance for broader `meta` operations. broader imported C-binding support may interleave with later gates.
+  - [x] mixed metadata-local execution checkpoint: ordinary and generic procedures retain runtime scalar/pointer inputs and effects alongside erased explicit/inferred type, array and record locals. owned snapshots preserve sequential field/index/whole updates, saved copies, generated runtime storage, constant branches, bounded construction loops, static exits and scoped metadata cleanup. runtime branches/loops create independent metadata locals; optional/collection captures keep their runtime bindings. constant tagged/optional metadata selection specializes only the selected body. runtime-dependent metadata still requires fully constant-input execution, and runtime paths cannot mutate enclosing metadata snapshots. interpreter/native `-O0`/`-O2`, imported private nominal leaves, source/session disposal and repeat compilation retain ownership and diagnostics. mutable metadata borrowing and broader constant materialization remain open.
+  - [ ] remaining gate: mutable metadata borrowing, broader constant materialization (including address-bearing untagged unions, nonnull data pointers and mutable slices), plus remaining existing-library acceptance for broader `meta` operations. broader imported C-binding support may interleave with later gates.
 - [ ] remaining source constructs: multiline strings. boolean and optional-capture conditional expressions, yielding value blocks, `yield`, compound updates and bitwise operators are covered above. examples: `source/parser/parse.hon`, `source/llvm/runtime.hon`.
 - [ ] standard-library milestone: compile/run a multi-package program exercising existing allocation and IO, including error cleanup; no replacement miniature standard library.
 - [ ] native driver integration: required C ABI declarations, `process.Init` startup arguments/IO, actual CLI exit statuses, file loading, temporary files and spawning Clang. Honey-generated programs currently accept only parameterless `main` and print its result; Bro's bootstrap startup support is not Honey backend support.