codegraph complexity --file returns empty functions[] for Lua files

[carlos-alm]

Context

Discovered during Titan audit (phase: gauntlet, date: 2026-07-02).

Description

codegraph complexity --file <f> --health -T --json returns functions:[] for every Lua file in the repo (tests/benchmarks/resolution/tracer/lua-tracer.lua and all 4 tests/benchmarks/resolution/fixtures/lua/*.lua files), even though codegraph where --file correctly extracts all Lua functions/parameters for the same files. Lua is listed as a supported LANGUAGE_REGISTRY language and symbol extraction clearly works — the gap is specific to the complexity-metrics engine not handling the Lua node kinds it is given, producing a false no-functions result rather than an error.

Additional Context

Repro:

codegraph complexity --file tests/benchmarks/resolution/tracer/lua-tracer.lua --health -T --json
codegraph where --file tests/benchmarks/resolution/tracer/lua-tracer.lua --json

The first command returns an empty functions array; the second correctly lists all Lua functions/parameters in the same file.

Source

• Titan phase: gauntlet
• Severity: bug
• Category: codegraph

[carlos-alm]

Engine-parity note: verified this isn't currently a native/WASM divergence — Lua is absent from the complexity language table on both sides (COMPLEXITY_RULES in src/ast-analysis/rules/index.ts lists only javascript/typescript/tsx/python/go/rust/java/csharp/ruby/php; the match lang_id arm at crates/codegraph-core/src/ast_analysis/complexity.rs:432-440 covers the identical 8-language set). So both engines agree today, just by both being wrong.

That means the fix must add a Lua entry to both tables in the same change — adding it to only one (e.g. shipping a TS-only fix) would turn this from "consistently unsupported" into a genuine native/WASM output divergence, which is worse. Please wire Lua into crates/codegraph-core/src/ast_analysis/complexity.rs alongside whatever TS-side rule config is added, and verify codegraph complexity --file <lua file> returns identical non-empty results under --engine native and --engine wasm before closing.