Initial commit: watch-together phases 0-4 + presence hardening, internet-tested

README.md

@@ -0,0 +1,28 @@
+# sync_relay_project
+
+Watch-together desktop app (working title). One binary, three modes:
+
+- **Client** — GUI Join, sync WS + mpv. No server code runs.
+- **Server+Client (Host)** — GUI Host starts `packages/server` in-process,
+  listens on a port, self-connects via loopback. Host must open ports.
+  Clients never open ports.
+- **Headless** — `watch.exe --headless`, same server package, no window.
+
+v1 order: links support (shared http(s) media URL, Syncplay-style sync)
+first, file relay (server-proxied bytes, whitelist case) after.
+Jellyfin native + auto-update are deferred as their own undertakings.
+
+Layout:
+
+```
+/packages/core      protocol, sync engine, messages (pure Dart, no Flutter)
+/packages/server    room + media HTTP endpoint (pure Dart, no Flutter)
+/apps/desktop       Flutter app embedding packages/server (the ONE binary)
+/tool               spikes + harnesses (range_logger, shaper, fake_viewer, e2e_check)
+/deploy             systemd unit, notes
+/docs               PROTOCOL.md, ARCHITECTURE.md, mpv-http-contract.md, ROADMAP.md
+```
+
+Phases + status: `docs/ROADMAP.md`. Session handoff: `HANDOFF.md` (root).
+
+Enforcement: `core` and `server` must have zero Flutter imports (tested).