refactor: integrate compilation-owned identifier interning

README.md

@@ -65,6 +65,8 @@ range bounds that are compound or unary expressions require their own parenthese
 
 name resolution (`@source/sema`) runs after parsing. it predeclares package names and each block's direct locals, allowing forward references and mutually recursive functions. parameters and top-level function-body locals share a scope; each conditional arm and loop body introduces a child scope whose names do not escape it. signatures resolve names in the enclosing package scope. shadowing is forbidden, including reuse of builtin type names (`int`, `float`, `i64`, `f64`, `usize`, `bool`, `string`, `void`); sibling scopes may independently reuse names.
 
+identifier interning is compilation-owned: initialize a `strpool.StringPool`, pass it to `lexer.scan` and `sema.resolve` before the diagnostic store, and release it after lowering. scanning interns identifier spellings once per pool; parsing preserves their IDs in compact AST storage, exposed through `ast.name_id`, while retaining source spans for diagnostics. name resolution keys scopes by those IDs and interns builtin names into the same pool, so identifier hashing and equality do not scan spelling bytes. IDs are meaningful only within their originating pool; independent compilations may assign the same numeric ID to different names. interning failures propagate as infrastructure errors rather than producing an invalid identifier ID. IR retains no pool dependency.
+
 `sema.resolve` returns an owned binding table indexed by AST `NodeId`, without modifying the AST. `sema.binding` identifies a declaration, builtin type, or invalid binding carrying its diagnostic ID; nodes with no binding return `.none`. release the result with `sema.deinit`. unknown names and duplicate declarations add source-spanned diagnostics; invalid syntax retains its existing diagnostic identity. same-scope duplicates retain the first declaration for recovery, while forbidden inner declarations invalidate that name's uses rather than silently binding them to an outer declaration.
 
 type checking (`@source/sema/check`) runs after name resolution. `check.check` borrows the AST and binding table and returns owned per-node types and interned array descriptors; query with `check.type_of` and `check.array_type`, and release with `check.deinit`. declarations infer their initializer types, including forward references and function aliases; function types identify the declaration supplying the callable signature. annotations support builtin types and fixed arrays; type names are not ordinary values. `void` is valid as a function result, not as a parameter or stored value.