fix(calls): DM-aware rejoin toast, and no rejoining a DM call that ended (#302)

After a reload during a DM call the toast said "You were in the call in
Bob Builder"; it now says "You were in a call with Bob Builder". DM
calls are never auto-rejoined (it could ring the other person), and if
they have left by the time you tap, the toast says "Call ended" instead
of starting a new, ringing call.

Fixes #302

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

src/app/utils/callRejoin.test.ts

@@ -1,6 +1,12 @@
 import { describe, it } from 'node:test';
 import assert from 'node:assert/strict';
-import { CALL_REJOIN_MAX_AGE_MS, decideRejoin, RejoinContext } from './callRejoin';
+import {
+  CALL_REJOIN_MAX_AGE_MS,
+  decideRejoin,
+  othersInCall,
+  rejoinToastBody,
+  RejoinContext,
+} from './callRejoin';
 
 const base: RejoinContext = {
   record: {
@@ -54,3 +60,21 @@ describe('decideRejoin', () => {
     });
   });
 });
+
+it('decideRejoin: DM calls are never auto-rejoined, only offered (#302)', () => {
+  assert.deepEqual(decideRejoin({ ...base, mode: 'auto', dm: true }), {
+    action: 'ask',
+    roomId: '!r',
+  });
+  assert.deepEqual(decideRejoin({ ...base, mode: 'auto' }), { action: 'auto', roomId: '!r' });
+});
+
+it('rejoinToastBody and othersInCall (#302)', () => {
+  assert.equal(
+    rejoinToastBody('Bob Builder', true),
+    'You were in a call with Bob Builder before the restart. Tap to rejoin.',
+  );
+  assert.match(rejoinToastBody('Voice Lounge', false), /in the call in Voice Lounge/);
+  assert.equal(othersInCall(['@me:x'], '@me:x'), false);
+  assert.equal(othersInCall(['@me:x', '@bob:x'], '@me:x'), true);
+});