fix(threads): viewing a room no longer reads threads you don't follow (#314)

A passive read (just looking at the room) sent a threaded receipt for
every unread thread you don't follow, so the Threads panel's Unread
filter and Mark all read only ever worked for followed threads.
Decision (2026-10-19): leave them unread until opened, but stop
counting unfollowed threads toward the room's unread dot
(getUnreadInfo subtracts them like muted threads; a mention makes a
thread followed, so highlights are never hidden). isThreadFollowed
moves to utils/room. Adds a Playwright regression.

Fixes #314

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/utils/notifications.test.ts

@@ -169,7 +169,7 @@ test('private receipt flag uses ReadPrivate', async () => {
 // follows unread; an explicit mark-as-read still clears everything.
 const sender = (userId: string) => ({ getSender: () => userId });
 
-test('passive: a thread I replied in stays unread; main receipt is scoped to main', async () => {
+test('passive: threads stay unread, followed or not; main receipt is scoped to main (#314)', async () => {
   const mine = thread('$mine', evt('$r1'), { hasCurrentUserParticipated: true });
   const other = thread('$other', evt('$r2'));
   const { mx, calls } = setup({
@@ -181,10 +181,9 @@ test('passive: a thread I replied in stays unread; main receipt is scoped to mai
   await markAsRead(mx, '!r:server', false, { passive: true });
   assert.deepEqual(
     calls.map((c) => [c.eventId, c.unthreaded]),
-    [
-      ['b', false], // main-scoped: unthreaded would also read $mine's reply
-      ['$r2', false],
-    ],
+    // main-scoped (unthreaded would read the threads' replies), and no thread
+    // receipts: [Gitea #314] unfollowed threads used to be read silently.
+    [['b', false]],
   );
 });
 
@@ -203,7 +202,7 @@ test('passive: threads I started or was mentioned in stay unread', async () => {
   assert.equal(calls.length, 0);
 });
 
-test('passive: no followed thread unread → main receipt stays unthreaded', async () => {
+test('passive: an unfollowed unread thread is left unread too (#314)', async () => {
   const other = thread('$other', evt('$r2'), { rootEvent: sender('@bob:server') });
   const { mx, calls } = setup({
     timeline: [evt('a'), evt('b')],
@@ -214,10 +213,16 @@ test('passive: no followed thread unread → main receipt stays unthreaded', asy
   await markAsRead(mx, '!r:server', false, { passive: true });
   assert.deepEqual(
     calls.map((c) => [c.eventId, c.unthreaded]),
-    [
-      ['b', true],
-      ['$r2', false],
-    ],
+    [['b', false]],
+  );
+});
+
+test('passive: no thread unread → main receipt stays unthreaded', async () => {
+  const { mx, calls } = setup({ timeline: [evt('a'), evt('b')], readUpTo: 'a', threads: [] });
+  await markAsRead(mx, '!r:server', false, { passive: true });
+  assert.deepEqual(
+    calls.map((c) => [c.eventId, c.unthreaded]),
+    [['b', true]],
   );
 });
 
@@ -249,9 +254,10 @@ test('passive: the thread open in the panel is left to the panel', async () => {
     threadUnread: { $open: 1, $other: 1 },
   });
   await markAsRead(mx, '!r:server', false, { passive: true, openThreadId: '$open' });
+  // The open thread is left to the panel, and [#314] the other one stays unread.
   assert.deepEqual(
     calls.map((c) => c.eventId),
-    ['$r2'],
+    [],
   );
 });