Resolve invitees via /state and accept 'invite' membership

For chats where we sent an opening message but the recipient never
accepted, /sync drops the room with no heroes and the recipient is
in state as m.room.member with membership:'invite' — not 'join'.
chat.reddit.com's web UI labels these rooms with the invitee anyway,
because it reads the full room state.

  - roomToActiveChat now accepts 'invite' membership in addition to
    'join' when scanning member-join state events.
  - enrichUsernames pass 2 hits /_matrix/client/v3/rooms/{id}/state
    first (cheap, returns all member events including invites) and
    only falls back to /messages history if /state yields nothing.
  - Added MatrixClient.getRoomFullState to back that lookup.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/services/chat/matrix/client.ts

@@ -276,6 +276,19 @@ export class MatrixClient {
     return res.joined;
   }
 
+  /**
+   * Returns the room's full state — every state event, including
+   * m.room.member entries with `membership: 'invite'` for chats the
+   * recipient hasn't accepted yet. Used to recover usernames for chats
+   * where /sync omitted heroes and state.
+   */
+  async getRoomFullState(roomId: string): Promise<MatrixTimelineEvent[]> {
+    return this.request<MatrixTimelineEvent[]>(
+      'GET',
+      `/_matrix/client/v3/rooms/${encodeURIComponent(roomId)}/state`,
+    );
+  }
+
   /** Returns the room's m.room.name content if set, else null. */
   async getRoomName(roomId: string): Promise<string | null> {
     try {

src/services/chat/service.ts

@@ -830,7 +830,14 @@ export class ChatService {
       if (ev.type !== 'm.room.member') continue;
       const stateKey = (ev as { state_key?: string }).state_key;
       const membership = (ev.content as { membership?: string }).membership;
-      if (membership === 'join' && stateKey && stateKey !== this.matrix.userId) {
+      // Include 'invite' too — for outgoing chats the recipient never
+      // accepted, their MXID is only in state as an invite, not a join.
+      // chat.reddit.com's web UI reads the same to display the invitee.
+      if (
+        (membership === 'join' || membership === 'invite') &&
+        stateKey &&
+        stateKey !== this.matrix.userId
+      ) {
         memberJoins.push(stateKey);
       }
     }
@@ -1028,9 +1035,10 @@ export class ChatService {
     }
 
     // Pass 2 — chats still stuck on 'unknown' (or a bare MXID) didn't get a
-    // t2 ID from /sync heroes/state/timeline. Try to mine one from /messages:
-    // a single 'b' page is enough to surface the recipient's MXID on any
-    // room that has ever exchanged a message.
+    // t2 ID from /sync heroes/state/timeline. Try /state first — it returns
+    // every m.room.member event including 'invite'-membership ones, which is
+    // how chat.reddit.com's web UI names rooms the recipient never accepted.
+    // Fall back to mining a /messages page if /state somehow yields nothing.
     for (const chat of this.cache.get()) {
       if (!chat.roomId) continue;
       if (this.unresolvableRooms.has(chat.roomId)) continue;
@@ -1039,30 +1047,48 @@ export class ChatService {
         chat.username === 'unknown' ||
         chat.username.startsWith('@');
       if (!needsLookup) continue;
+      let t2: string | undefined;
       try {
-        const res = await this.withAuth(() =>
-          this.matrix.getRoomMessages(chat.roomId!, { limit: 20, dir: 'b' }),
-        );
-        const otherSender = res.chunk?.find(
-          (e) => e.sender && e.sender !== this.matrix.userId,
-        )?.sender;
-        const t2 = otherSender?.match(/^@(t2_[^:]+):/)?.[1];
-        if (t2) {
-          const bare = t2.replace(/^t2_/, '');
-          const known = this.t2ToUsername.get(bare);
-          chat.username = known ?? t2;
-          if (!chat.roomName || chat.roomName === 'unknown' || chat.roomName.startsWith('@')) {
-            chat.roomName = chat.username;
-          }
-          dirty = true;
-        } else {
-          // No other party has ever sent a message here (we sent an opener
-          // that was never accepted, etc). Don't retry every sync.
-          this.unresolvableRooms.add(chat.roomId);
-        }
+        const state = await this.withAuth(() => this.matrix.getRoomFullState(chat.roomId!));
+        const otherMember = state.find((e) => {
+          if (e.type !== 'm.room.member') return false;
+          const sk = (e as { state_key?: string }).state_key;
+          const membership = (e.content as { membership?: string }).membership;
+          return (
+            sk &&
+            sk !== this.matrix.userId &&
+            (membership === 'join' || membership === 'invite')
+          );
+        }) as { state_key?: string } | undefined;
+        t2 = otherMember?.state_key?.match(/^@(t2_[^:]+):/)?.[1];
       } catch (err) {
+        this.logger.debug(`[chat] /state lookup failed for ${chat.roomId}:`, err);
+      }
+      if (!t2) {
+        try {
+          const res = await this.withAuth(() =>
+            this.matrix.getRoomMessages(chat.roomId!, { limit: 20, dir: 'b' }),
+          );
+          const otherSender = res.chunk?.find(
+            (e) => e.sender && e.sender !== this.matrix.userId,
+          )?.sender;
+          t2 = otherSender?.match(/^@(t2_[^:]+):/)?.[1];
+        } catch (err) {
+          this.logger.debug(`[chat] /messages lookup failed for ${chat.roomId}:`, err);
+        }
+      }
+      if (t2) {
+        const bare = t2.replace(/^t2_/, '');
+        const known = this.t2ToUsername.get(bare);
+        chat.username = known ?? `t2_${bare}`;
+        if (!chat.roomName || chat.roomName === 'unknown' || chat.roomName.startsWith('@')) {
+          chat.roomName = chat.username;
+        }
+        dirty = true;
+      } else {
+        // Neither /state nor /messages surfaced a t2 — give up on this room
+        // so we don't keep hammering the homeserver every sync.
         this.unresolvableRooms.add(chat.roomId);
-        this.logger.debug(`[chat] history lookup failed for ${chat.roomId}:`, err);
       }
     }