feat(dwarf): internal functions get their real names from the wasm name section (#394)

[avrabe]

What

Tier-1.x follow-up to #557 (#394): DW_TAG_subprogram DW_AT_name for internal (non-exported) functions was the synthetic func_N, because the wasm name custom section (function-names subsection) was never parsed. A backtrace through a panic helper showed func_7 instead of the real developer-facing name.

Before → after (msgq_put_359.wasm, --relocatable --debug-line, subprogram DW_AT_names):

func idx	before	after
6 (exported)	z_impl_k_msgq_put	z_impl_k_msgq_put
7 (internal)	func_7	core::panicking::panic_const::panic_const_add_overflow::hacec966df230a78f
8 (internal)	func_8	gale::msgq::put_decide::h36409b4bbfd25a9a
9 (exported)	gale_k_msgq_put_decide	gale_k_msgq_put_decide
10 (internal)	func_10	core::panicking::panic_fmt::h6651313c3e2c6c2f

How

• wasm_decoder.rs: parse the name custom section (KnownCustom::Name → Name::Function map) into a new FunctionOps.debug_name, applied after the parse loop (the custom section trails the code section). Best-effort by design — debug metadata must never fail a compile. Both decode_wasm_module and decode_wasm_functions.
• synth-cli/main.rs: thread debug_name through ElfFunction into the subprogram compose. Name priority: name-section > export name > func_N. DWARF-only — the symbol table and relocation labels keep using the export-name-or-func_N name, so linkability is untouched.
• dwarf_line.rs: doc-only (the priority contract on SubprogramInfo.name).

Oracle (RED → GREEN)

New Oracle G in dwarf_debug_line_emit_394.rs (emitted_subprogram_names_use_name_section_for_internal_functions_394): ground truth (name section + export section) parsed from the fixture at runtime with wasmparser directly (non-circular). Asserts (a) ≥1 compiled internal function's DIE carries its real name-section name, and (b) zero synthetic func_N names remain (the fixture names every function). RED before — the pre-change binary emits func_7/func_8/func_10 and none of the internal real names appear anywhere in the object; GREEN after.

Gates (exit-code-verified)

• DWARF oracles A–G: 8/8 pass
• frozen_codegen_bytes: 3/3 — .text byte-identical (purely additive DWARF metadata; .symtab unchanged)
• cargo test --workspace --exclude synth-verify: 90 suites, 1677 passed, 0 failed (exit 0)
• cargo fmt --check: exit 0
• cargo clippy --workspace --all-targets -- -D warnings: exit 0 (full workspace incl. synth-verify)

🤖 Generated with Claude Code

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