ec-node: WebTransport publish + web hang-watch

evolution/proposals/ECP-0063-cloudflare-moq-webtransport.md

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+# ECP-0063: Cloudflare MoQ Relay + WebTransport-Only Web Watch
+
+Status: Draft
+
+## Decision
+
+Adopt Cloudflare's MoQ relay preview as the default "global" distribution layer and make the web watcher path WebTransport-only.
+
+Concrete changes:
+
+1. `ec-node` gains a WebTransport MoQ publisher path that can publish a live CMAF (fMP4) stream to a relay URL (default: `https://relay.cloudflare.mediaoverquic.com/`).
+2. `every.channel` (the deployed static site) becomes a real web watcher by embedding a WebTransport-capable MoQ player component (`<hang-watch>`).
+3. The existing WebRTC/WS bootstrap directory/relay remains temporarily for compatibility, but is treated as deprecated once MoQ/WebTransport is stable.
+
+## Motivation
+
+The project goal is one-to-many live streaming at global scale without rebuilding a bespoke stateful SFU stack.
+
+MoQ over WebTransport moves the core system boundary to:
+- publisher produces timed objects (CMAF fragments),
+- relays cache/fanout,
+- subscribers fetch via a single WebTransport session.
+
+This aligns the "global watcher" story with an infrastructure-native model rather than point-to-point rendezvous.
+
+## Scope
+
+In scope for this ECP:
+- "Watch from the web" using WebTransport to a MoQ relay.
+- "Publish from a node" to the relay, using ffmpeg to create fMP4 fragments.
+- A shareable link format for `every.channel` to open a specific relay + broadcast name.
+
+Out of scope (explicitly deferred):
+- Global discovery/index of broadcasts.
+- Manifest signing / Merkle availability / anti-junk (separate ECPs already exist).
+- Safari support guarantees (implement anyway; provide guidance/flag notes).
+- Multi-variant ladders and ABR (follow-on ECP once single-variant publish/watch works end-to-end).
+
+## Technical Notes
+
+### Relay default
+
+Default relay endpoint is:
+- `https://relay.cloudflare.mediaoverquic.com/`
+
+Nodes may override via CLI flags for self-hosted relays or future Cloudflare relay endpoints.
+
+### Web player
+
+Use the `@kixelated/hang` web component:
+- `<hang-watch url="..." name="..." controls>`
+
+This is WebTransport + WebCodecs based, and is expected to interoperate with Cloudflare's current relay preview.
+
+### Share link
+
+Web share link:
+- `https://every.channel/watch?url=<relay-url>&name=<broadcast-name>`
+
+## Rollout / Reversibility
+
+- Keep existing `/api/*` bootstrap endpoints during migration.
+- Make the web site prefer MoQ/WebTransport; keep legacy paths hidden behind "advanced" until removed.
+- Reversible by switching the deployed assets back to the previous UI build, and/or pointing users at the legacy paths.
+