feat(channels): add Facebook Messenger and Pancake channel integrations (#731)

Add two new channel implementations for Facebook Fanpage (comment + Messenger
auto-reply, first inbox DM) and Pancake/pages.fm (multi-platform inbox via
Facebook, Zalo, Instagram, TikTok, WhatsApp, LINE).

Key features:
- Facebook: comment auto-reply, Messenger auto-reply, first inbox DM,
  HMAC-SHA256 webhook verification, multi-page webhook routing
- Pancake: multi-platform inbox, outbound echo dedup with HTML normalization,
  race-condition-safe echo fingerprinting, platform-aware formatting
- Bootstrap skip: pre-fill USER.md from channel metadata (Pancake)
- SanitizeDisplayName across all channels (defense in depth)

Code audit fixes:
- Fix truncateForTikTok byte→rune slicing (UTF-8 corruption)
- Fix empty message.ID shared dedup slot (silent message loss)
- Fix DisplayName markdown injection in buildPrefilledUser
- Consolidate duplicate ChannelMeta type (agent→bootstrap)
- Compile-time interface assertions, alphabetical type constants
- Per-message logs demoted to slog.Debug, errors.As for wrapped errors
- UI: alphabetical channel ordering, complete config schemas
- Remove deprecated WhatsApp bridge_url, fix nested error parsing

cmd/gateway.go

@@ -20,6 +20,8 @@ import (
 	"github.com/nextlevelbuilder/goclaw/internal/eventbus"
 	kg "github.com/nextlevelbuilder/goclaw/internal/knowledgegraph"
 	"github.com/nextlevelbuilder/goclaw/internal/channels/discord"
+	"github.com/nextlevelbuilder/goclaw/internal/channels/facebook"
+	"github.com/nextlevelbuilder/goclaw/internal/channels/pancake"
 	"github.com/nextlevelbuilder/goclaw/internal/channels/feishu"
 	slackchannel "github.com/nextlevelbuilder/goclaw/internal/channels/slack"
 	"github.com/nextlevelbuilder/goclaw/internal/channels/telegram"
@@ -417,6 +419,8 @@ func runGateway() {
 		instanceLoader.RegisterFactory(channels.TypeZaloPersonal, zalopersonal.FactoryWithPendingStore(pgStores.PendingMessages))
 		instanceLoader.RegisterFactory(channels.TypeWhatsApp, whatsapp.FactoryWithDB(pgStores.DB, pgStores.PendingMessages, "pgx"))
 		instanceLoader.RegisterFactory(channels.TypeSlack, slackchannel.FactoryWithPendingStore(pgStores.PendingMessages))
+		instanceLoader.RegisterFactory(channels.TypeFacebook, facebook.Factory)
+		instanceLoader.RegisterFactory(channels.TypePancake, pancake.Factory)
 		if err := instanceLoader.LoadAll(context.Background()); err != nil {
 			slog.Error("failed to load channel instances from DB", "error", err)
 		}

cmd/gateway_callbacks.go

@@ -30,8 +30,8 @@ func buildEnsureUserProfile(as store.AgentStore) agent.EnsureUserProfileFunc {
 // isNew=true seeds all files; isNew=false only seeds if user has zero files
 // (avoids re-seeding BOOTSTRAP.md after auto-cleanup on server restart).
 func buildSeedUserFiles(as store.AgentStore) agent.SeedUserFilesFunc {
-	return func(ctx context.Context, agentID uuid.UUID, userID, agentType string, isNew bool) error {
-		_, err := bootstrap.SeedUserFiles(ctx, as, agentID, userID, agentType, !isNew)
+	return func(ctx context.Context, agentID uuid.UUID, userID, agentType string, isNew bool, channelMeta *bootstrap.ChannelMeta) error {
+		_, err := bootstrap.SeedUserFiles(ctx, as, agentID, userID, agentType, !isNew, channelMeta)
 		return err
 	}
 }

cmd/gateway_consumer_helpers.go

@@ -91,6 +91,18 @@ func extractSessionMetadata(msg bus.InboundMessage, peerKind string) map[string]
 	return meta
 }
 
+// buildPancakeSessionLabel returns "Pancake:{senderName}:{pageName}" with non-empty parts only.
+func buildPancakeSessionLabel(senderName, pageName string) string {
+	label := "Pancake"
+	if senderName != "" {
+		label += ":" + senderName
+	}
+	if pageName != "" {
+		label += ":" + pageName
+	}
+	return label
+}
+
 // buildAnnounceOutMeta builds outbound metadata for announce messages so that
 // Send() can route replies to the correct forum topic or DM thread.
 func buildAnnounceOutMeta(localKey string) map[string]string {

cmd/gateway_consumer_normal.go

@@ -108,6 +108,12 @@ func processNormalMessage(
 		}
 	}
 
+	// Set session label for Pancake channels: "Pancake:{SenderName}:{PageName}"
+	if msg.Metadata["pancake_mode"] != "" {
+		label := buildPancakeSessionLabel(msg.Metadata["display_name"], msg.Metadata["page_name"])
+		deps.SessStore.SetLabel(ctx, sessionKey, label)
+	}
+
 	// Auto-collect channel contacts for the contact selector.
 	// Skip internal senders (system:*, notification:*, teammate:*, ticker:*, session_send_tool).
 	if deps.ContactCollector != nil && msg.SenderID != "" && !bus.IsInternalSender(msg.SenderID) {

cmd/gateway_managed.go

@@ -157,6 +157,7 @@ func wireExtras(
 		ContextFileLoader:      contextFileLoader,
 		BootstrapCleanup:       buildBootstrapCleanup(stores.Agents),
 		CacheInvalidate:        buildCacheInvalidate(contextFileInterceptor),
+		DefaultTimezone:        appCfg.Cron.DefaultTimezone,
 		InjectionAction:        injectionAction,
 		MaxMessageChars:        appCfg.Gateway.MaxMessageChars,
 		CompactionCfg:          appCfg.Agents.Defaults.Compaction,