matrix: judge-gated Shape B inject — closes lift-suite tail issues

Lift suite run #004 left two unresolved tail issues:
- Q6 ("Forklift loader") ↔ Q7 ("Hazmat warehouse, cold storage")
  swap recordings as warm top-1 because their embeddings are within
  0.20 cosine of each other. Distance gate can't tell them apart.
- Q9 + Q15 lose paraphrase recovery when qwen2.5 rephrases past the
  0.20 threshold. Distance says "drift too far"; sometimes the drift
  is real (skip), sometimes the paraphrase is still on-domain (don't
  want to skip).

Multi-coord run #008's judge re-rating proved the LLM can
distinguish: Q3 crane case landed at distance 0.23 (looks tight)
but rating 1 (irrelevant). The judge sees domain mismatch the
embedder doesn't.

This commit lifts that pattern into the matrix substrate. Shape B
inject now optionally routes every candidate through a judge gate
before the rank insert lands. Distance + judge BOTH have to approve.

internal/matrix/playbook.go:
- InjectPlaybookMisses signature gains a query string + an
  optional InjectGate. nil gate preserves pre-judge-gating
  behavior (current tests already pass with nil).
- New InjectGate interface + InjectGateFunc adapter for tests
  and non-LLM callers.
- Per-candidate gate.Approve(query, hit) call inserted between
  the dedup and the inject. Rejected candidates skip silently;
  injected count reflects post-gate decision.

internal/matrix/judge.go (new, ~140 lines):
- LLMJudgeGate calls an Ollama-shape /api/chat endpoint with the
  same 1-5 staffing-rubric prompt that worked in multi_coord
  run #008. fail-closed on HTTP/JSON errors (don't inject if
  judge can't speak — better miss than wrong-domain).
- NewLLMJudgeGate returns nil when URL or Model is empty,
  matching InjectGate's nil-means-no-judge semantics.

internal/matrix/retrieve.go:
- SearchRequest gains JudgeURL, JudgeModel, JudgeMinRating
  fields. Run() builds an LLMJudgeGate when set; passes nil
  otherwise. Backward compatible — existing callers see no
  behavior change.

Tests:
- TestInjectPlaybookMisses_GateRejectsCandidate (rejectAll → 0
  injected, even with tight distance)
- TestInjectPlaybookMisses_GateApprovesCandidate (approveAll →
  same as nil-gate behavior)
- TestInjectPlaybookMisses_GateSeesCorrectQuery (gate receives
  CURRENT query + RECORDED query separately so it can score
  the (current, candidate) pair)
- All 5 existing inject tests updated to new signature

go test ./internal/matrix → all 8 inject tests pass.
go test ./internal/matrix ./internal/shared ./cmd/{matrixd,
queryd,pathwayd,observerd} → all green.

STATE_OF_PLAY:
- OPEN item #1 (judge-gated injection) closed.
- DO NOT RELITIGATE adds the substrate-level judge-gate lock.
- OPEN list now 5 rows (was 6).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/matrix/retrieve.go

@@ -84,7 +84,15 @@ type SearchRequest struct {
 	PlaybookTopK        int            `json:"playbook_top_k,omitempty"`
 	PlaybookMaxDistance       float64        `json:"playbook_max_distance,omitempty"`
 	PlaybookMaxInjectDistance float64        `json:"playbook_max_inject_distance,omitempty"`
-	MetadataFilter            map[string]any `json:"metadata_filter,omitempty"`
+	// JudgeURL: when set, every Shape B injection candidate is
+	// rated by an LLM at this Ollama-shape /api/chat endpoint
+	// (chatd's /v1/chat works too). Candidates with rating <
+	// JudgeMinRating are skipped. Empty = no judge gate (current
+	// behavior — distance-only filter).
+	JudgeURL       string `json:"judge_url,omitempty"`
+	JudgeModel     string `json:"judge_model,omitempty"`
+	JudgeMinRating int    `json:"judge_min_rating,omitempty"`
+	MetadataFilter map[string]any `json:"metadata_filter,omitempty"`
 	// ExcludeIDs filters out specific worker IDs post-retrieval.
 	// Real-world driver: a coordinator places 200 workers at a
 	// contract, then mid-day the client asks for a different set —
@@ -289,8 +297,14 @@ func (r *Retriever) Search(ctx context.Context, req SearchRequest) (*SearchRespo
 			if maxInjectDist <= 0 {
 				maxInjectDist = float32(DefaultPlaybookMaxInjectDistance)
 			}
+			// Optional LLM judge gate (per OPEN item #1). nil when
+			// JudgeURL/JudgeModel are unset → distance-only filter.
+			var gate InjectGate
+			if g := NewLLMJudgeGate(req.JudgeURL, req.JudgeModel, req.JudgeMinRating, nil); g != nil {
+				gate = g
+			}
 			var injected int
-			resp.Results, injected = InjectPlaybookMisses(resp.Results, hits, maxInjectDist)
+			resp.Results, injected = InjectPlaybookMisses(req.QueryText, resp.Results, hits, maxInjectDist, gate)
 			resp.PlaybookInjected = injected
 			if injected > 0 {
 				// Re-sort + truncate after injection. ApplyPlaybookBoost