Tasks 5-8: new `kebab-parse-code` crate with three infrastructure modules
for the code ingest framework. Ships lang.rs (extension→language identifier
mapping), repo.rs (.git walk-up via gix 0.70 for RepoMeta), and skip.rs
(BUILTIN_BLACKLIST, is_generated_file, is_oversized). 14 integration tests
across three test files, all passing; clippy -D warnings clean.
Note: gix pinned to 0.70 (not 0.83 as originally suggested) because 0.83
fails to compile against Rust 1.94.1 due to non-exhaustive match patterns
in gix-hash. 0.70 resolves cleanly and has identical head_name/head_id API.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
