Phase 3: rooms, local only

Implements PLAN.md Phase 3: the roomserver, the room half of storage, the
Client-Server room endpoints and the admin room endpoints. A client can now
create a room, invite, join, leave, kick, ban, send messages and state,
redact, name a room with an alias and find one in the public directory.
Nothing talks to another server; every operation that would need to is
refused with a message that says so rather than a bare M_FORBIDDEN.

roomserver: one input pipeline every event goes through, whatever sent it —
validate, authorise, resolve, persist, emit. The rules are not
reimplemented here; internal/matrix is pure library code and this is what
connects it to a database and to a room's history. The Client-Server
handlers do no authorisation of their own, deliberately: whether Alice may
kick Bob is a question about the room's power levels, and the one place
that is answered correctly is the authorisation rules inside the pipeline.

A mutex per room serialises writers. Two events racing into one room would
each read the same forward extremities, both become one, and fork the room
for no reason — which would then need state resolution to put back
together. State resolution is wired in anyway for the multi-extremity
case. It is unreachable from outside in this phase, and the alternative is
a pipeline that authorises against one arbitrary branch of a fork without
saying so.

Room versions 3 to 12 all work and are each tested end to end. Version 12
earns that coverage: its room ID is the create event's own ID, its create
event carries no room_id, and the create event is excluded from every other
event's auth_events — so the state auth.Check is given is the event's
auth_events plus the create event, which that version identifies by room ID
rather than citing.

createRoom sends the spec's events in the spec's order, each authorised
against what the ones before it produced. A failure part-way leaves an
incomplete room, which is the lesser evil: the alternative is holding every
event of a new room in memory and writing them in one transaction, making
the pipeline that authorises them a special case. The one failure a second
client can cause at any time, an alias clash, takes the room row back out.

Redactions stay two decisions, as the spec keeps them. The rules let almost
any redaction into the room; whether it applies to its target is a separate
test, run inside the same transaction as the redaction itself so that a
client holding an event ID can always read the stripped event.

storage: events keyed by event ID rather than by a surrogate, since an
event ID appears in prev_events, auth_events, state snapshots and client
requests alike. Stream ordering comes from a counter row bumped inside the
write transaction, because a PostgreSQL sequence is explicitly not
transactional and a rolled-back write would leave a hole in the stream that
/sync would have to be taught to skip. State snapshots are stored per event
and deduplicated by content hash, so the table grows with state changes
rather than with traffic — and that is what makes "the state after a
forward extremity" answerable at all. The room's listing columns are
denormalised onto its row because the public directory orders every
published room by member count and pages the result, which cannot be done
by reading each room's state in turn.

Federation-disabled behaviour from PLAN.md section 3 is enforced here.
Restricted joins are the exception that works: the rule needs a signature
from the authorising user's server verified, and while federation is off
that server is always this one.

adminapi: room list and detail, purge, force-leave, and room and event
counters on the dashboard. clientapi gains its own rate-limit buckets for
createRoom and for joining, both of which write events rather than read
them.

Tested against the real event core and a real database rather than fakes:
what is under test is whether an event this server signs is one the
authorisation rules accept, and a fake of either would only prove that the
pipeline calls what the fake expects. The storage tests run against both
SQL drivers. docs/rooms.md describes the pipeline, the storage decisions
and the known gaps — chief among them that history visibility is
room-level rather than per-event, and that /sync still reports no rooms,
both of which belong with the event stream in Phase 4.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

server/internal/clientapi/sync.go

@@ -7,8 +7,7 @@ import (
 	"github.com/dariuszjaniak/warp/server/internal/userapi"
 )
 
-// syncResponse is the subset of the /sync body that is meaningful before
-// there are any rooms.
+// syncResponse is the subset of the /sync body this build can fill in.
 type syncResponse struct {
 	NextBatch   string          `json:"next_batch"`
 	Rooms       syncRooms       `json:"rooms"`
@@ -34,27 +33,29 @@ type syncDeviceLists struct {
 	Left    []string `json:"left"`
 }
 
-// syncPlaceholderToken is the only stream position Phase 1 can be at.
+// syncPlaceholderToken is the only stream position this build has.
 //
 // It is a real token shape rather than an empty string so that a client
-// storing it and sending it back as ?since= gets the same answer, which is
-// the correct one: nothing has happened.
+// storing it and sending it back as ?since= gets the same answer.
 const syncPlaceholderToken = "s0_0"
 
-// handleSync implements GET /_matrix/client/v3/sync as far as Phase 1 can.
+// handleSync implements GET /_matrix/client/v3/sync as far as this build
+// can.
 //
-// This is a placeholder, and deliberately a working one. There are no rooms
-// until Phase 3 and no event streams until Phase 4, so an empty sync is not
-// a lie — it is the complete state of this server. What it buys in the
-// meantime is the thing every client and the test suite check first: that a
-// valid token syncs and a revoked one does not. Without it, "logging out
-// invalidates the session" cannot be observed at all.
+// It is a placeholder, and since Phase 3 it is an incomplete answer rather
+// than a complete one: there are rooms now, and this reports none of them.
+// Filling it in means the event stream — stream tokens, incremental deltas,
+// long polling, filters and lazy-loaded members — which is the syncapi of
+// PLAN.md phase 4, and which replaces this wholesale.
 //
-// Phase 4 replaces this wholesale with the syncapi: stream tokens, long
-// polling, filters and lazy-loaded members.
+// It stays because of what it does buy: a valid token syncs and a revoked
+// one does not, which is the first thing every client and the test suite
+// check, and which cannot be observed at all without an endpoint here. A
+// client can meanwhile see its rooms through /joined_rooms and read them
+// through /rooms/{roomID}/state. See docs/rooms.md.
 func (c *ClientAPI) handleSync(w http.ResponseWriter, _ *http.Request, _ userapi.Authenticated) error {
 	// The `timeout` parameter is ignored rather than honoured: blocking for
-	// 30 seconds to return a response that cannot change would hold a
+	// 30 seconds to return a response this build cannot change would hold a
 	// connection open for nothing.
 	httputil.WriteJSON(w, http.StatusOK, syncResponse{
 		NextBatch: syncPlaceholderToken,