feat(audio): wire Scribe STT + legacy bridge in gateway setup

Register ElevenLabs Scribe and proxy STT providers in gateway initialization. Auto-wire legacy STT bridge from existing channel STTProxyURL configs. Implement setupAudioExtras() with RegisterSTT and SetSTTChain calls. Maintains backward compat with per-channel configs.

cmd/gateway_agents.go

@@ -315,4 +315,16 @@ func setupAudioExtras(cfg *config.Config, mgr *tts.Manager) {
 			slog.Info("audio.music: minimax registered")
 		}
 	}
+
+	// ElevenLabs STT (Scribe v2) — reuse TTS credentials. Registered as tenant-scope
+	// default; per-request tenant override lands via builtin_tools[stt] in Phase 5
+	// channel migration. Legacy per-channel STTProxyURL is bridged separately.
+	if ellKey != "" {
+		mgr.RegisterSTT(elevenlabs.NewSTTProvider(elevenlabs.Config{
+			APIKey:  ellKey,
+			BaseURL: ellBase,
+		}))
+		mgr.SetSTTChain([]string{"elevenlabs", "proxy"})
+		slog.Info("audio.stt: elevenlabs registered")
+	}
 }

cmd/gateway_setup.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/google/uuid"
 
+	"github.com/nextlevelbuilder/goclaw/internal/audio"
 	"github.com/nextlevelbuilder/goclaw/internal/bootstrap"
 	"github.com/nextlevelbuilder/goclaw/internal/bus"
 	"github.com/nextlevelbuilder/goclaw/internal/config"
@@ -139,7 +140,8 @@ func setupToolRegistry(
 	if ttsMgr == nil {
 		ttsMgr = tts.NewManager(tts.ManagerConfig{})
 	}
-	setupAudioExtras(cfg, ttsMgr) // Phase 3: registers Music + SFX providers.
+	setupAudioExtras(cfg, ttsMgr)      // Phase 3: registers Music + SFX providers.
+	audio.BridgeLegacySTT(ttsMgr, cfg) // Phase 4: bridge per-channel STTProxyURL → channel-scoped providers.
 
 	// Audio generation tool — backed by audio.Manager (Music + SFX).
 	toolsReg.Register(tools.NewCreateAudioTool(ttsMgr))