feat(sync): replace WS+DO transport with unified HTTP sync

Replace the WebSocket + Cloudflare Durable Object architecture with a
single POST /sync endpoint. The CLI now operates autonomously with local
state (tasks.json) and syncs bidirectionally via adaptive-interval HTTP
polling (3s watching, 60s idle).

- Remove transport_ws, transport_hybrid, transport_http (~2,600 lines)
- Add SyncClient with adaptive interval loop
- Add LocalState for CLI-side task persistence
- Add TaskStateFromUpdate() helper (DRY)
- Extract finalize() to deduplicate processTask/processTaskRetry
- Consolidate shortID() into agent.ShortID (was in 3 packages)
- Wire GetActiveCount so `unarr status` shows active tasks
- Remove poll_interval, heartbeat_interval, ws_url from config
- Simplify ProgressReporter (sync replaces direct HTTP reporting)

internal/cmd/config_menu.go

@@ -311,21 +311,10 @@ func configConnection(cfg *config.Config) error {
 	).Run()
 }
 
-func configAdvanced(cfg *config.Config) error {
-	return huh.NewForm(
-		huh.NewGroup(
-			huh.NewInput().
-				Title("Poll interval").
-				Description("How often to check for new tasks (e.g. 30s, 1m)").
-				Value(&cfg.Daemon.PollInterval).
-				Validate(validateDuration),
-			huh.NewInput().
-				Title("Heartbeat interval").
-				Description("How often to send heartbeat to server (e.g. 30s, 1m)").
-				Value(&cfg.Daemon.HeartbeatInterval).
-				Validate(validateDuration),
-		),
-	).Run()
+func configAdvanced(_ *config.Config) error {
+	// Sync intervals are adaptive (3s watching, 60s idle) — no user-facing config needed.
+	fmt.Println("No advanced settings to configure. Sync intervals are automatic.")
+	return nil
 }
 
 // ── Validators ──────────────────────────────────────────────────────