richer formatting

TODO.md

@@ -686,8 +686,8 @@
     evaluation; runtime-dependent values remain invalid in comptime contexts
   - runtime-only behavior is rejected in comptime: external/bodyless `c_func`,
     writable globals, and materializing comptime storage pointers/slices as runtime memory
-  - v1 keeps integer-only `$N` specialization keys; aggregate comptime parameters
-    and stable aggregate serialization are deferred
+  - milestone 39 extends specialization keys from integer/type/string values to
+    recursively stable values while keeping runtime ABI erasure unchanged
 
 27.8 source-defined mutable runtime globals (implemented)
   - allow mutable global declarations in Brolang source for process-global runtime
@@ -867,7 +867,23 @@
 38. place every intrinsic behind direct unqualified `name!(...)` syntax, freeing the bare names for
     user functions (implemented)
 
-39. aggregate comptime parameters and richer formatting
+39. stable comptime values and richer formatting (implemented)
+  - comptime parameters accept booleans, integers, floats, types, immutable bytes,
+    enums, fixed arrays, records/tuples, optionals, and tagged unions recursively
+  - canonical specialization keys include deterministic type identity, exact float bits,
+    byte contents, ordered aggregate children, optional state, and active union variants;
+    FNV-1a fingerprints accelerate lookup while exact key comparison handles collisions
+  - equal structural values reuse specializations and stable emitted names, distinct values
+    specialize separately, aggregate inference uses exact type-factory provenance, and all
+    comptime parameters remain erased from the runtime ABI
+  - undefined values, pointers, functions, general slices, fallibles, ranges, and untagged
+    unions diagnose that they have no stable comptime identity
+  - `@std/meta.TypeInfo.enum` carries declaration-ordered `EnumInfo.fields`, enabling enum
+    formatting through `field!` without runtime reflection metadata
+  - `io.print` and `debug.print` retain their APIs and expand `{}`, `{s}`, `{d}`, `{b}`,
+    `{o}`, `{x}`, `{X}`, `{c}`, and `{e}` at comptime; `{{` and `}}` remain escapes
+  - integer output uses one base-aware 65-byte stack buffer; float output uses fixed-buffer
+    libc `snprintf` with 32-bit and 64-bit general/scientific precision and propagates failure
 
 ## A word on unchecked casts