codegen: thread the function name explicitly instead of ambient current_fn_name

[0xGeorgii]

Fixes #172. Stacked on #278 (167-refactoring-shared-statement-walker) — merge that first (both live in compiler.rs).

Removes the mutable ambient Compiler::current_fn_name: String and threads the function name explicitly as fn_name: &str from visit_function_definition_body through the statement-lowering walker (lower_statement → lower_block/lower_if_statement/lower_loop_statement) to its sole runtime reader, the sret-return invariant panic in lower_sret_return.

• Plain &str threading, no context struct: there is exactly one reader, and this matches how arena/ctx/module_path already flow. The sibling current_fn_key is also ambient but out of current_fn_name Mutable State on Compiler #172's scope — left for a separate cleanup (noted intentionally).
• Latent-bug check (per the issue's ambient-context concern): none found — the field was written fresh per function and only read within that function's lowering; the empty-string init was unreachable as a read.
• Byte identity: golden suite green with zero regenerated expectations (542 codegen tests); the examiner independently built both branches and compiled the array-sret and struct-sret fixtures — identical SHA256. Full default-workspace cargo test 4359/0; default clippy clean, zero new pedantic findings vs baseline (990 = 990).

Confidence Score: 5/5

Safe to merge — purely mechanical refactoring with no behavioral change and byte-identical WASM output confirmed by the golden test suite.

The change removes a write-once-per-function ambient string field and replaces it with an explicit &str parameter. Every call site has been updated, the borrow lifetime is sound (the owning String lives in visit_function_definition for the duration of all nested calls), and the sole reader (the sret panic message) is unchanged in meaning. No logic paths were added or altered.

No files require special attention.

Important Files Changed

Filename	Overview
core/wasm-codegen/src/compiler.rs	Removes current_fn_name: String from Compiler, adds fn_name: &str parameter to five lowering functions; threading is mechanically correct and all call sites are updated.
CHANGELOG.md	Adds a correct changelog entry for #172 and the corresponding reference link; prose accurately describes the change.

_{Reviews (2): Last reviewed commit: "Merge branch 'main' into 172-refactoring..." | Re-trigger Greptile}

[codecov]

Codecov Report

❌ Patch coverage is 92.85714% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
core/wasm-codegen/src/compiler.rs	92.85%	2 Missing ⚠️

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