refactor(webapp): delete the relay, and everything it needed to survive

[ssowonny]

TL;DR

• −1,768 / +389. The co-editing relay is deleted, along with every mechanism that existed to compensate for it.
• Two browsers editing one file now converge instead of producing conflict copies.
• Solo mode is gone as a CRDT path — an unreachable hub leaves the editor open and saving, it just has no live collaboration.
• Conflict copies and If-Match stay: they guard the file from writers that never touch a CRDT at all.

What was deleted, and why each existed

The relay never parsed a frame, so nobody owned the document. Every property that needs an owner was faked somewhere else:

deleted	existed because
the seed claim	two clients seeding one file build two documents that duplicate every character on merge
seedClaimGrace	a claim that produced nothing left later joiners with a blank document the editor would write to the file
maxRoomBytes + rebuild	an append-only log grows without bound; a document does not
resync + replay-the-log reconnect	there was no state vector to diff against
announce / re-announce	awareness is relayed and never logged, so nobody could be discovered late
solo mode	— and this one cost a real user six characters (#234)

None of it is disabled. It's gone, because the property each piece was faking is now simply true.

Two things found while deleting

A stale If-Match with identical content is not a conflict, it's a late arrival. The check ran before the no-op check, so three clients sharing one document produced two conflict copies of text nobody disputed. Ordering them the other way is the whole fix.

stream_guard_test.go tested the streaming guard through /collab. That guard matters more than ever — it's what stops an unflushable writer handing back an empty 200 a client retries forever — so it now targets /events. A websocket is an upgrade, not a stream this guard applies to, which is the same distinction compression draws.

A test that changed meaning

concurrent-edit.spec.ts used to assert a relay-less editor's work was preserved beside a teammate's. It now asserts they converge: every character both people typed, in the file, no conflict copy needed.

stress spec, this morning:  3 paths, 4 versions  (two conflict copies)
stress spec, now:           1 paths, 2 versions

What stays, deliberately

Conflict copies and If-Match. They guard the file against an agent, the CLI, or a device syncing — writers that never touch a CRDT — and removing the relay doesn't close that door.

Verification

Full module: 12 packages ok. Editor e2e: 26 passed including two-person co-editing and the three-editor stress soak. Both architecture diagrams updated and parse-checked — the collabRoom note was the largest single block of "why this is hard" in either file, and is now one note about a hub that owns the document.

🤖 Generated with Claude Code