Vector retriever was disabled everywhere because it appeared to hang.
It was actually doing a first-time embedding index build for 57K files,
which takes ~60-90 min. Re-enable vector by increasing timeouts and
letting scope-aware retriever selection decide when vector is safe.
Changes:
- sift_search: retriever timeout 30s->300s, total 60s->600s
- codebase_search: total timeout 120s->600s
- warmup: retriever timeout 30s->300s, hard timeout 600s->3600s
- codebase_search now uses chooseSiftRetrievers() instead of hardcoded
bm25+phrase: repo-root -> bm25+phrase (fast), scoped subdirs -> vector
- Comments updated to reflect "slow first build" not "hang"
Tests: 178 files / 1845 tests, all pass.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
