feat: lifecycle broadcasts on signup_closed / cancelled / debating / completed

Phase 3 push-wakeup mechanism without adding a new push channel.
Topic state transitions now post short messages to the same Fabric
announce channel used for the initial signup announcement. Agents
subscribed to announce + not currently busy get woken via the
existing Phase 1 inbound path; busy-discard already filters
appropriately. No SSE, no per-agent DM fanout, no plugin changes —
reuses existing infra end-to-end.

Changes:
- ticker.go: after signup_close transition, broadcasts signup_closed
  (with pro/con/judge agent IDs + debate-start time) OR cancelled
  (with reason). After debate_start transition, broadcasts debating
  with debate-end time.
- announce.go: new PostLifecycleEvent helper - same headers/auth as
  PostTopicAnnouncement, different format.
- verdict.go: after successful judge submission, broadcasts completed
  with the judge id. Best-effort + async so a slow Fabric does not
  slow the judge response.
- routes.go: instantiates the announcer once + passes to VerdictHandler.

Workflow participate-debate step 5 should be updated to expect
wakeups instead of polling - separate follow-up edit on lyn/ClawSkills.

internal/fabric/announce.go

@@ -115,6 +115,47 @@ func formatAnnouncement(id, title, summary string,
 	)
 }
 
+// PostLifecycleEvent broadcasts a non-signup state change to the
+// announce channel. The agents' Fabric inbound + busy-discard
+// (Phase 1) handles per-agent wakeup gating — no per-agent fanout
+// needed from this side. Sole purpose is to let agents see "your
+// debate moved to X" without polling.
+//
+// Currently called for: signup_closed (with allocated camps),
+// cancelled, debating-start, completed. Format is plain text with the
+// topic_id so agents' workflows can parse and route.
+func (a *Announcer) PostLifecycleEvent(ctx context.Context, topicID, title, kind, summary string) error {
+	if !a.Enabled() {
+		log.Printf("announce: lifecycle skipped (fabric coupling not configured) topic=%s kind=%s", topicID, kind)
+		return nil
+	}
+	body := map[string]any{
+		"content": fmt.Sprintf("📣 **[%s]** %s [%s]\n%s", kind, title, topicID, summary),
+	}
+	raw, _ := json.Marshal(body)
+	url := fmt.Sprintf("%s/api/channels/%s/messages",
+		trimRightSlash(a.cfg.GuildBaseURL), a.cfg.ChannelID)
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(raw))
+	if err != nil {
+		return err
+	}
+	req.Header.Set("content-type", "application/json")
+	req.Header.Set("authorization", "Bearer "+a.cfg.BotBearerToken)
+	req.Header.Set("x-fabric-system-key", a.cfg.SystemAPIKey)
+	resp, err := a.client.Do(req)
+	if err != nil {
+		log.Printf("announce: lifecycle POST %s failed: %v", url, err)
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode >= 300 {
+		b, _ := io.ReadAll(io.LimitReader(resp.Body, 1024))
+		log.Printf("announce: lifecycle POST %s -> %d body=%s", url, resp.StatusCode, string(b))
+		return fmt.Errorf("lifecycle post: status %d", resp.StatusCode)
+	}
+	return nil
+}
+
 func trimRightSlash(s string) string {
 	for len(s) > 0 && s[len(s)-1] == '/' {
 		s = s[:len(s)-1]

internal/httpapi/handlers/verdict.go

@@ -1,27 +1,30 @@
 package handlers
 
 import (
+	"context"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"net/http"
 	"time"
 
 	"github.com/go-chi/chi/v5"
 
 	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/auth"
+	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/fabric"
 	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/models"
 	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/store"
 )
 
 type VerdictHandler struct {
-	db       *struct{} // placeholder; we don't use the raw conn directly here
-	topics   *store.TopicStore
-	camps    *store.CampStore
-	verdicts *store.VerdictStore
+	topics    *store.TopicStore
+	camps     *store.CampStore
+	verdicts  *store.VerdictStore
+	announcer *fabric.Announcer // optional; nil-safe via Enabled() check
 }
 
-func NewVerdictHandler(t *store.TopicStore, c *store.CampStore, v *store.VerdictStore) *VerdictHandler {
-	return &VerdictHandler{topics: t, camps: c, verdicts: v}
+func NewVerdictHandler(t *store.TopicStore, c *store.CampStore, v *store.VerdictStore, ann *fabric.Announcer) *VerdictHandler {
+	return &VerdictHandler{topics: t, camps: c, verdicts: v, announcer: ann}
 }
 
 type submitVerdictBody struct {
@@ -114,6 +117,18 @@ func (h *VerdictHandler) Submit(w http.ResponseWriter, r *http.Request) {
 		w.Header().Set("x-warn", "verdict saved but status update failed: "+err.Error())
 	}
 
+	// Lifecycle broadcast — completed event. Best-effort; runs async
+	// outside the request context so a slow Fabric doesn't slow the
+	// judge's response.
+	if h.announcer != nil {
+		go func(t *fabric.Announcer, tID, title string, judge string) {
+			summary := fmt.Sprintf("verdict published by judge=%s. Use dialectic_view_verdict to see the structured result.", judge)
+			if err := t.PostLifecycleEvent(context.Background(), tID, title, "completed", summary); err != nil {
+				// silent failure; the announcer logs internally
+			}
+		}(h.announcer, verdict.TopicID, topic.Title, caller.ID)
+	}
+
 	writeJSON(w, http.StatusCreated, map[string]any{
 		"id":             verdict.ID,
 		"topic_id":       verdict.TopicID,

internal/httpapi/routes.go

@@ -11,6 +11,7 @@ import (
 
 	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/auth"
 	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/config"
+	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/fabric"
 	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/httpapi/handlers"
 	"git.hangman-lab.top/hzhang/Dialectic.Backend/internal/store"
 )
@@ -62,7 +63,13 @@ func Mount(cfg *config.Config, db *sqlx.DB, version string) http.Handler {
 	topicsH := handlers.NewTopicsHandler(topicStore)
 	signupsH := handlers.NewSignupsHandler(topicStore, signupStore)
 	argsH := handlers.NewArgumentsHandler(topicStore, campStore, roundStore, argStore)
-	verdictH := handlers.NewVerdictHandler(topicStore, campStore, verdictStore)
+	announcer := fabric.NewAnnouncer(fabric.AnnounceConfig{
+		GuildBaseURL:   cfg.FabricGuildBaseURL,
+		ChannelID:      cfg.FabricAnnounceChannelID,
+		SystemAPIKey:   cfg.FabricSystemAPIKey,
+		BotBearerToken: cfg.FabricBotBearerToken,
+	})
+	verdictH := handlers.NewVerdictHandler(topicStore, campStore, verdictStore, announcer)
 	adminH := handlers.NewAdminHandler(db, cfg.AgentAPIKeyPepper, cfg.DialecticAdminAPIKey)
 
 	// Routes.

internal/orchestrator/ticker.go

@@ -2,6 +2,7 @@ package orchestrator
 
 import (
 	"context"
+	"fmt"
 	"log"
 	"math/rand"
 	"time"
@@ -117,6 +118,10 @@ func (t *Ticker) tickOnce(ctx context.Context) {
 	if err := t.transitionByStatus(ctx, now,
 		models.TopicStatusSignupOpen, "signup_close_at",
 		func(ctx context.Context, tx *sqlx.Tx, topicID string) error {
+			topic, err := t.topics.GetByID(ctx, topicID)
+			if err != nil {
+				return err
+			}
 			signups, err := t.signups.ListByTopic(ctx, topicID)
 			if err != nil {
 				return err
@@ -128,6 +133,10 @@ func (t *Ticker) tickOnce(ctx context.Context) {
 					models.TopicStatusCancelled, res.CancelReason, topicID)
 				log.Printf("orchestrator: topic %s cancelled at signup_close: %s",
 					topicID, res.CancelReason)
+				if err == nil {
+					go t.broadcastLifecycle(topic, "cancelled",
+						fmt.Sprintf("debate cancelled at signup close — %s", res.CancelReason))
+				}
 				return err
 			}
 			if err := t.camps.WriteAllocation(ctx, tx, topicID, res.Allocation); err != nil {
@@ -139,6 +148,14 @@ func (t *Ticker) tickOnce(ctx context.Context) {
 			log.Printf("orchestrator: topic %s allocated pro=%s con=%s judge=%s",
 				topicID,
 				res.Allocation[models.CampPro], res.Allocation[models.CampCon], res.Allocation[models.CampJudge])
+			if err == nil {
+				go t.broadcastLifecycle(topic, "signup_closed",
+					fmt.Sprintf("camps allocated — pro=%s con=%s judge=%s. Debate starts at %s",
+						res.Allocation[models.CampPro],
+						res.Allocation[models.CampCon],
+						res.Allocation[models.CampJudge],
+						topic.DebateStartAt.UTC().Format("2006-01-02 15:04 UTC")))
+			}
 			return err
 		}); err != nil {
 		log.Printf("orchestrator: signup_open→signup_closed scan: %v", err)
@@ -148,6 +165,10 @@ func (t *Ticker) tickOnce(ctx context.Context) {
 	if err := t.transitionByStatus(ctx, now,
 		models.TopicStatusSignupClosed, "debate_start_at",
 		func(ctx context.Context, tx *sqlx.Tx, topicID string) error {
+			topic, err := t.topics.GetByID(ctx, topicID)
+			if err != nil {
+				return err
+			}
 			if _, err := tx.ExecContext(ctx,
 				`UPDATE topics SET status = ? WHERE id = ?`,
 				models.TopicStatusDebating, topicID); err != nil {
@@ -155,10 +176,15 @@ func (t *Ticker) tickOnce(ctx context.Context) {
 			}
 			// Round 0 inserted within the tx — if commit fails we don't
 			// leak a half-state.
-			_, err := tx.ExecContext(ctx,
+			_, err = tx.ExecContext(ctx,
 				`INSERT INTO rounds (id, topic_id, round_no) VALUES (UUID(), ?, 0)`,
 				topicID)
 			log.Printf("orchestrator: topic %s entered debating; round 0 opened", topicID)
+			if err == nil {
+				go t.broadcastLifecycle(topic, "debating",
+					fmt.Sprintf("debate is live — pro/con post arguments; judge stays mostly silent until debate_end_at (%s). Use participate-debate workflow.",
+						topic.DebateEndAt.UTC().Format("2006-01-02 15:04 UTC")))
+			}
 			return err
 		}); err != nil {
 		log.Printf("orchestrator: signup_closed→debating scan: %v", err)
@@ -220,6 +246,20 @@ func (t *Ticker) applyOne(ctx context.Context, topicID string,
 	return tx.Commit()
 }
 
+// broadcastLifecycle wraps the announcer's lifecycle-event post with
+// the standard signup_closed / cancelled / debating / completed
+// formats. Best-effort; runs in its own goroutine outside any tx.
+func (t *Ticker) broadcastLifecycle(topic *models.Topic, kind, summary string) {
+	if topic == nil {
+		return
+	}
+	if err := t.announcer.PostLifecycleEvent(
+		context.Background(), topic.ID, topic.Title, kind, summary,
+	); err != nil {
+		log.Printf("orchestrator: lifecycle broadcast topic=%s kind=%s failed: %v", topic.ID, kind, err)
+	}
+}
+
 func (t *Ticker) broadcastAnnouncement(topic *models.Topic) {
 	if topic == nil {
 		return