Root cause: the sift binary's phrase retriever hangs indefinitely when
queried against the full repo-root scope (57K+ files). Earlier tests
mistook this for a general slowness, but isolated testing confirms:
- bm25 alone on repo root: works (1m 30s cold, instant warm)
- phrase alone on repo root: hangs forever
- bm25+phrase on repo root: hangs forever (phrase path blocks)
- all retrievers on scoped subdirs: work correctly
The earlier Rust panic was from a corrupted cache state left by killing
a mid-build vector process. After clearing the cache, bm25 alone works.
Fix: chooseSiftRetrievers now returns retrievers: "bm25" (not "bm25,phrase")
for repo-root scope. Scoped subdirs still get bm25+phrase+vector with
position-aware reranking.
Tests: updated 3 assertions in sift-retriever-scope.test.mjs.
Full suite: 183 files / 1958 tests pass.
Type check: clean.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
