test(search): expand FTS operator regression matrix

[ohdearquant]

Body:

• Problem: bug(db): single-quote in search query crashes FTS5 ("syntax error near '") #549 and the migration fix cover apostrophe and hyphen crashes, but the regression matrix does not yet cover the wider set of FTS5 operator-sensitive inputs across knowledge and generic KG search surfaces.
• Proposed fix: add tests for quotes, parentheses, boolean operators, punctuation-heavy terms, and mixed Unicode/ASCII inputs across both search paths.
• Acceptance criteria: tests prove special characters do not crash; search returns a valid empty or non-empty result; both knowledge and KG text search surfaces are covered; the tests cite bug(db): single-quote in search query crashes FTS5 ("syntax error near '") #549 as historical context without reopening the shipped fix.
• Affected crates/ADRs: crates/khive-pack-knowledge/tests/fixes.rs:1128, crates/khive-db/src/stores/text.rs:1212.

---

Source: khive-improvement-survey show — proposed backlog (propose-only synthesis). Dedup: NEW.

[ohdearquant]

Resolved in PR #601 (v0.2.3). Normalized 0-1 scores, default rerank=true, FTS5 hardening, warm latency bench.