rtti: retain named-module initializer hashes

[borisbat]

Summary

• resolve generated structure initializers from the module's simple-name function index
• select the zero-argument function returning the exact structure before recording its mangled-name hash
• add a named-module RTTI regression that compares StructInfo.init_mnh with FuncInfo.hash

Validation

• focused interpreter regression: 1 passed
• focused AOT regression: 1 passed
• formatter verification: clean
• linter: 0 issues, 0 errors
• full preflight: 13 passed, 0 failed (local tool/DLL-lock skips left to CI)

[Copilot]

Pull request overview

This PR fixes how RTTI records a structure’s generated initializer mangled-name hash (StructInfo.init_mnh) when the structure lives in a named module, and adds a regression test to ensure the hash matches the corresponding function’s FuncInfo.hash.

Changes:

• Resolve generated structure initializers via the module’s functionsByName index (simple-name lookup) instead of findFunction on an unmangled name.
• Select the matching zero-argument function that returns the exact structure before recording init_mnh.
• Add a named-module RTTI regression test and document it in the tests README.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
tests/README.md	Adds the new RTTI regression test to the language tests list.
tests/language/test_rtti_init_mnh.das	New regression ensuring StructInfo.init_mnh matches the initializer FuncInfo.hash in a named module.
src/ast/ast_debug_info_helper.cpp	Updates RTTI debug-info emission to find the correct initializer function in named modules and store its mangled-name hash.

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