feat(chat): add sidebar search for conversations

frontend/tests/chat-collaboration.test.cjs

@@ -72,6 +72,34 @@ test('only member rooms enter normal chat, with separate keys, groups and unread
   assert.equal(ui.run('decoratedRooms.value.some(r => r.id === "admin-only")'), false)
 })
 
+test('searching the sidebar preserves the open conversation and draft, including hidden-room matches', async t => {
+  const ui = setup(fixture(url => {
+    if (url.endsWith('/project-rooms')) return { rooms: [{ key: 'project_1', name: 'Büro Süd', projectNumber: 'P-2026-42', exists: true, type: 'project' }] }
+    if (url.endsWith('/direct-rooms')) return { rooms: [{ key: 'direct_1', name: 'Anna Müller', email: 'anna@example.test', exists: true, type: 'direct' }] }
+  }))
+  t.after(ui.close)
+  ui.mount()
+  await settle()
+  ui.run('draft.value = "Noch nicht gesendet"; roomSearch.value = "  BÜRO  2026-42  "')
+  assert.equal(ui.run('groupedRooms.value.length'), 1)
+  assert.equal(ui.run('groupedRooms.value[0].rooms[0].key'), 'project_1')
+  ui.run('roomSearch.value = "muller ANNA@"')
+  assert.equal(ui.run('groupedRooms.value[0].rooms[0].key'), 'direct_1')
+  await ui.run('setRoomHidden(decoratedRooms.value.find(room => room.key === "direct_1"), true)')
+  assert.equal(ui.run('groupedRooms.value.length'), 0)
+  assert.equal(ui.run('filteredHiddenRooms.value[0].key'), 'direct_1')
+  ui.run('roomSearch.value = "kein Treffer"')
+  await settle()
+  assert.equal(ui.run('filteredRooms.value.length'), 0)
+  assert.equal(ui.run('filteredHiddenRooms.value.length'), 0)
+  assert.equal(ui.run('activeRoom.value.key'), 'allgemein')
+  assert.equal(ui.run('messages.value[0].body'), 'Interne Nachricht')
+  assert.equal(ui.run('draft.value'), 'Noch nicht gesendet')
+  ui.run('roomSearch.value = ""')
+  assert.equal(ui.run('groupedRooms.value.length'), 3)
+  assert.equal(ui.run('hiddenRooms.value[0].key'), 'direct_1')
+})
+
 test('opening a collaboration deep link never provisions, reads or sends through native chat APIs', async t => {
   const ui = setup(fixture(), { room: 'collaboration:shared-room' })
   t.after(ui.close)