Upgrade RAG pipeline with Python scraper and hybrid search

[muzaffermahi]

No description provided.

[Doorman11991]

Reviewed this against #63 — they're two attempts at the same RAG harness from the same author.

Recommending this one (#64) and closing #63. Every shared file is byte-for-byte identical between the two PRs. The differences:

• Upgrade RAG pipeline with Python scraper and hybrid search #64: 1 clean squashed commit, descriptive title, 11 files.
• Codex/create rag coding harness 6vogkz #63: 7 iteration commits, auto-generated title, 12 files — the extra file is src/rag/github_scraper.js, which is dead code (not imported anywhere; the actual scraping is done by scripts/rag_scraper.py, shared by both PRs).

Verified locally: merging this PR into current master builds cleanly (npm run build) and the full suite passes including the new test/rag.test.js (RAG snippet-chunking test green). The in-isolation CI only ran Socket Security because the branch predates the provider-import fix on master, but the merge result is sound since this PR doesn't touch src/compiled/providers/.

Merging.