#37 Language bar: obey gitignore, skip binaries

Context: Owner QA — language bar on code page counts binaries (inflating "other"). Cleanest: obey .gitignore + skip binary blobs. Tasks:

1. Language walk: respect repo .gitignore (git check-ignore or parse top-level .gitignore; prefer git ls-files-style listing via gitx so ignored/untracked junk never counts) + skip NUL-containing blobs (binary sniff: first 8KB contains \0 → excluded, still downloadable).
2. "other" bucket: keep, but only for real text files with unmapped extensions. Binaries never appear anywhere in the math.
3. Tests: fixture with gitignored dir + binary file + code files asserts ignored/binary bytes excluded and percentages sum to counted text only. Success rubric:

• Demo code page: no binary bytes in language math; gitignored paths excluded. Swarm: Owl. Branch m6/lang-ignore.