fix(p5-1): apply deferred review items — App reuse + expand_path hoist + nits
- kb-app: promote App to pub, add open_with_config / search / ask methods
so kb-eval (and future TUI) can amortize embedder + vector store + LLM
cold-start across many queries on one App instance. Memoization is
per-instance via OnceLock; *_with_config free functions delegate.
- kb-config: add canonical expand_path helper + 8 unit tests; drop the
4 duplicate copies in kb-store-sqlite, kb-store-vector, kb-embed-local,
kb-eval (net: -6 duplicate tests, +8 canonical tests).
- kb-eval: extract elapsed_ms_u32 helper, drop redundant tracing debug
log (with_context already names path on error), replace dead-port :1
test with bind-then-release ephemeral port.
Verified: cargo clippy --workspace --all-targets -D warnings clean,
all crate tests green (kb-app 12+3 ignored, kb-eval 11, kb-config 17,
kb-store-sqlite 33, kb-store-vector 7+8 AVX-gated, kb-embed-local 7+7).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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