bug(parity): native engine produces ast_nodes, WASM engine does not

[carlos-alm]

Problem

The native Rust engine extracts AST nodes (calls, strings, regex, await, throw, new) via walk_ast_nodes() in each language extractor, but the WASM engine has no equivalent extraction. This causes tests/integration/build-parity.test.ts > produces identical ast_nodes to fail when both engines are available.

Context

The WASM call-AST extraction was previously removed as dead code (see PR #686). The parity test was masked because the native engine always crashed on null visibility serialization before this was fixed in #693.

Expected behavior

Both engines should produce identical ast_nodes output. Per CLAUDE.md: "Both engines must produce identical results."

Fix

Either:

1. Add AST node extraction to the WASM engine's extractors to match native
2. Or ensure the native engine's ast_nodes output is consumed by the WASM build path via a separate enrichment step