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)

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.5.6] - 2026-04-07
+
+
+### Fixed
+
+- **ws**: add ping/pong keepalive and read deadline to detect zombie connections
 ## [0.5.5] - 2026-04-07
 
 
@@ -17,6 +23,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - **daemon**: cancel watch reporter on stream switch and re-notify ready
+
+### Other
+
+- **release**: 0.5.5
 ## [0.5.4] - 2026-04-07
 
 
@@ -153,6 +163,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - remove UPX compression (antivirus false positives, startup penalty)
 - add -s -w -trimpath to Makefile, add build-small target with UPX
+[0.5.6]: https://github.com/torrentclaw/unarr/compare/v0.5.5...v0.5.6
 [0.5.5]: https://github.com/torrentclaw/unarr/compare/v0.5.4...v0.5.5
 [0.5.4]: https://github.com/torrentclaw/unarr/compare/v0.5.3...v0.5.4
 [0.5.3]: https://github.com/torrentclaw/unarr/compare/v0.5.2...v0.5.3