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.ts

@@ -67,6 +67,8 @@ export type RejoinContext = {
   ownMemberDevices: string[];
   /** Number of call memberships in the room, ours included. */
   memberCount: number;
+  /** A DM call: rejoining one may ring the other person. */
+  dm?: boolean;
 };
 
 export type RejoinDecision = { action: 'none' } | { action: 'ask' | 'auto'; roomId: string };
@@ -83,5 +85,18 @@ export function decideRejoin(ctx: RejoinContext): RejoinDecision {
   // Nobody there any more (our own stale membership doesn't count).
   const others = ctx.memberCount - ctx.ownMemberDevices.length;
   if (others <= 0) return { action: 'none' };
+  // [Gitea #302] Never rejoin a DM call on our own: if the other person has
+  // just left, starting it again would ring them. Ask instead.
+  if (ctx.dm && mode === 'auto') return { action: 'ask', roomId: record.roomId };
   return { action: mode, roomId: record.roomId };
 }
+
+/** Pure: whether anyone but us is still in the call (by call membership). */
+export const othersInCall = (memberUserIds: string[], myUserId: string): boolean =>
+  memberUserIds.some((u) => u !== myUserId);
+
+/** The rejoin toast's text; DMs name the person rather than "the call in <room>". */
+export const rejoinToastBody = (roomName: string | undefined, dm: boolean): string =>
+  dm
+    ? `You were in a call with ${roomName ?? 'them'} before the restart. Tap to rejoin.`
+    : `You were in the call in ${roomName ?? 'a room'} before the restart. Tap to rejoin.`;