Ingest blocks on large directories — add SKIP_DIRS, file-count guard, lower max size to 2MB

[four-bytes-robby]

Problem

Brain ingest blocks (appears hung) on large directories like ~/session-sw6 (2.6GB, 55K files). Walk finds ~5K files to process (mostly .js/.php), processing them all causes apparent hang.

Changes

1. loader.ts — SKIP_DIRS: Added .opencode, docker, var, bundles, db-dumps to skip list
2. loader.ts — EXTENSION_LANG_MAP: Added .twig → "twig" mapping
3. index.ts — MAX_FILE_SIZE: Lowered from 10MB to 2MB (no useful source file exceeds this)
4. index.ts — File-count guard: Hard abort at >5000 files, warning at >500
5. package.json: Version bump 1.7.4 → 1.7.5

How to test

bun run build succeeds, dist/four-opencode-brain.js updated.

[four-bytes-robby]

Fixed by PR #129 (SKIP_DIRS, file-count guard, lower max size to 2MB) — closing as completed.