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/reload_unix.go

@@ -7,7 +7,6 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
-	"time"
 
 	"github.com/torrentclaw/unarr/internal/agent"
 	"github.com/torrentclaw/unarr/internal/config"
@@ -19,7 +18,8 @@ type ReloadableConfig struct {
 }
 
 // startReloadWatcher listens for SIGUSR1 and reloads config.
-// Only intervals are hot-reloadable (speeds require torrent client restart).
+// With the sync-based architecture, intervals are fixed (3s watching, 60s idle).
+// Hot-reload now mainly serves as a signal to re-read config for future settings.
 func startReloadWatcher(rc *ReloadableConfig) {
 	sigCh := make(chan os.Signal, 1)
 	signal.Notify(sigCh, syscall.SIGUSR1)
@@ -28,24 +28,11 @@ func startReloadWatcher(rc *ReloadableConfig) {
 		for range sigCh {
 			log.Println("Received SIGUSR1, reloading config...")
 
-			cfg, err := config.Load("")
+			_, err := config.Load("")
 			if err != nil {
 				log.Printf("Config reload failed: %v", err)
 				continue
 			}
-			cfg.ApplyEnvOverrides()
-
-			// Update poll interval
-			if d, _ := time.ParseDuration(cfg.Daemon.PollInterval); d > 0 && rc.Daemon.PollTicker != nil {
-				rc.Daemon.PollTicker.Reset(d)
-				log.Printf("  Poll interval: %s", d)
-			}
-
-			// Update heartbeat interval
-			if d, _ := time.ParseDuration(cfg.Daemon.HeartbeatInterval); d > 0 && rc.Daemon.HeartbeatTicker != nil {
-				rc.Daemon.HeartbeatTicker.Reset(d)
-				log.Printf("  Heartbeat interval: %s", d)
-			}
 
 			log.Println("Config reloaded successfully")
 		}