Coherence pass — PRD/PHASES updates, config snapshot wired, unit tests

J flagged the audit: "make sure everything flows coherently, no
pseudocode or unnecessary patches or ignoring any particular part of
what we built." This is that pass.

PRD.md updates:
- Phase 19 refinement block — geo-filter + role-prefilter WIRED with
  citation density numbers (0.32 → 1.38, and 2 → 28 on same scenario).
- Phase 20 rewrite — mistral dropped, qwen3.5 + qwen3 local hot path,
  think:false as the key mechanical finding, kimi-k2.6 upgrade path.
- Phase 21 status block — think plumbing + cloud executor routing
  added after original commit.
- Phase 22 item B (cloud rescue) — pivot sanitizer, rescue verified
  1/3 on stress_01.
- Phase 23 NEW — staffer identity + tool_level + competence-weighted
  retrieval + kb_staffer_report. Auto-discovered worker labels called
  out with real numbers (Rachel Lewis 12× across 4 staffers).
- Phase 24 NEW — Observer/Autotune integration gap DOCUMENTED, not
  fixed. Observer has been idle at 0 ops for 3600+ cycles because
  scenarios hit gateway:3100 directly, bypassing MCP:3700 which the
  observer wraps. This is the honest "we're not using it in these
  tests" signal J surfaced. Fix deferred; gap visible now.

PHASES.md:
- Appended Phases 20-23 as checked, Phase 24 as unchecked gap.
- Updated footer count: 102 unit tests across all layers.
- Latest line updated with 14× citation lift + 46.4pt tool-asymmetry
  finding.

scenario.ts:
- snapshotConfig() was defined but never called. Now fires at every
  scenario start with a stable sha256 hash over the active model set +
  tool_level + cloud flags. config_snapshots.jsonl finally populates,
  which the error_corrections diff path needs to work correctly.

kb.test.ts (new): 4 signature invariant tests — stability across
unrelated fields (date, contract, staffer), sensitivity to role/city/
count changes, digest shape. All pass under `bun test`.

service.rs: 6 Rust extractor tests for extract_target_geo +
extract_target_role — basic, missing-state-returns-none, word
boundary (civilian != city), multi-word role, absent role, quoted
value parse. All pass under `cargo test -p vectord --lib extractor_tests`.

Dangling items now honestly documented rather than silently pending:
- Chunking cache (config/models.json SPEC, not wired) — flagged
- Playbook versioning (SPEC, not wired) — flagged
- Observer integration (WIRED but disconnected) — new Phase 24

crates/vectord/src/service.rs

@@ -2486,3 +2486,46 @@ async fn lance_build_scalar_index(
         Err(e) => Err((StatusCode::INTERNAL_SERVER_ERROR, e)),
     }
 }
+
+#[cfg(test)]
+mod extractor_tests {
+    use super::*;
+
+    #[test]
+    fn extract_target_geo_basic() {
+        let f = "role = 'Welder' AND city = 'Toledo' AND state = 'OH' AND CAST(availability AS DOUBLE) > 0.5";
+        assert_eq!(extract_target_geo(f), Some(("Toledo".into(), "OH".into())));
+    }
+
+    #[test]
+    fn extract_target_geo_missing_state_returns_none() {
+        let f = "role = 'Welder' AND city = 'Toledo'";
+        assert_eq!(extract_target_geo(f), None);
+    }
+
+    #[test]
+    fn extract_target_geo_word_boundary() {
+        // "civilian" contains "city" as a substring — must not match.
+        let f = "civilian_rank = 1 AND city = 'Toledo' AND state = 'OH'";
+        assert_eq!(extract_target_geo(f), Some(("Toledo".into(), "OH".into())));
+    }
+
+    #[test]
+    fn extract_target_role_basic() {
+        let f = "role = 'Welder' AND city = 'Toledo'";
+        assert_eq!(extract_target_role(f), Some("Welder".into()));
+    }
+
+    #[test]
+    fn extract_target_role_none_when_absent() {
+        let f = "city = 'Toledo' AND state = 'OH'";
+        assert_eq!(extract_target_role(f), None);
+    }
+
+    #[test]
+    fn extract_target_role_multi_word() {
+        let f = "role = 'Warehouse Associate' AND city = 'Chicago'";
+        assert_eq!(extract_target_role(f), Some("Warehouse Associate".into()));
+    }
+}
+