feat(orchestrator): agent-initiated ROTATE via handoff reason=manual (S11)

rotate() and TurnDecision now check the agent's own handoff for
meta.reason=="manual" before evaluating occupancy/turn-boundary — per
spec §5.3, that reason is itself the boundary signal ("a coherent unit
finished and the next is independent"), so it bypasses both checks and
releases immediately. Extracted the shared release-and-anchor-certify
tail into Coordinator.finishRelease so the manual path gets the same
anchor safety guarantee as the threshold path.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W1rkJ2hBMybnJctPbcy4tT

internal/orchestrator/rotation_test.go

@@ -257,6 +257,54 @@ func TestTurnDecision(t *testing.T) {
 			t.Fatalf("task state=%v ok=%v, want leased", got.State, ok)
 		}
 	})
+
+	// Agent-initiated ROTATE (spec §5.3): a handoff the agent wrote with
+	// reason=manual is itself the boundary signal ("a coherent unit
+	// finished and the next is independent") — it must release immediately,
+	// bypassing occupancy and the turn-boundary probe entirely, not wait for
+	// either to agree.
+	t.Run("manual reason bypasses occupancy and turn boundary", func(t *testing.T) {
+		a := &fakeAdapter{occupancy: 0, boundary: false}
+		c, st, task := newCoordinator(a)
+		artifactRef, err := st.PutArtifact([]byte("handoff"))
+		if err != nil {
+			t.Fatal(err)
+		}
+		a.ref = artifactRef
+		head, err := herdr.HeadSHA(repo)
+		if err != nil {
+			t.Fatal(err)
+		}
+		handoff := map[string]any{
+			"meta":   map[string]any{"id": "h2", "reason": "manual", "rotation_index": 0},
+			"anchor": map[string]any{"git_sha": head, "branch": "orchestra/t1"},
+			"goal":   "g", "done_when": []string{"x"}, "action": "prompt", "command": "go test ./...",
+		}
+		b, err := json.Marshal(handoff)
+		if err != nil {
+			t.Fatal(err)
+		}
+		handoffPath := repo + "/" + herdr.HandoffFile
+		if err := os.WriteFile(handoffPath, b, 0o644); err != nil {
+			t.Fatal(err)
+		}
+		t.Cleanup(func() { os.Remove(handoffPath) })
+
+		decision, err := c.TurnDecision(context.Background(), task.ID)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if decision != orchestrator.TurnRotateNow {
+			t.Fatalf("decision=%q want %q", decision, orchestrator.TurnRotateNow)
+		}
+		if a.releases == 0 {
+			t.Fatal("Release was never invoked for an agent-initiated manual rotate")
+		}
+		got, ok := st.Task(task.ID)
+		if !ok || got.State != domain.StateQueued {
+			t.Fatalf("task state=%v ok=%v, want queued", got.State, ok)
+		}
+	})
 }
 
 // TestStartBlocksOnInvalidPickup guards AUDIT.md's B6/Phase 4 item 4: