Add durable candidate funnel

tests/chat-service-cooldown.test.ts

@@ -31,7 +31,7 @@ function buildService() {
     path.join(os.tmpdir(), `chat-cache-${Date.now()}-${Math.random()}.json`),
   );
   const svc = new ChatService(matrix, logger, undefined, undefined, undefined, undefined, cache, undefined, undefined, authenticatedAccountAuth);
-  return { svc, logger };
+  return { svc, logger, matrix };
 }
 
 describe('ChatService invitation cooldown', () => {
@@ -82,6 +82,30 @@ describe('ChatService invitation cooldown', () => {
     expect(result).toBeNull();
   });
 
+  it('returns a retryable delivery result with the persisted cooldown deadline', async () => {
+    const { svc } = buildService();
+    svc.setInvitationCooldown(
+      new MatrixRateLimitError('429', 60_000, 'M_LIMIT_EXCEEDED', 'rate.foo'),
+    );
+    const cooldown = svc.getInvitationCooldown()!;
+
+    await expect(svc.startConversationDetailed('someuser', 'hi')).resolves.toEqual({
+      status: 'retryable',
+      reason: cooldown.reason,
+      retryAt: cooldown.until,
+    });
+  });
+
+  it('classifies recipients that reject chat requests as terminal', async () => {
+    const { svc, matrix } = buildService();
+    matrix.sendInitialDirectMessage = async () => {
+      throw new Error('some of the invited users do not accept chat requests');
+    };
+
+    await expect(svc.startConversationDetailed('someuser', 'hi', 't2_someuser'))
+      .resolves.toEqual({ status: 'terminal', reason: 'Recipient does not accept chat requests' });
+  });
+
   it('sendChatMessage short-circuits when a cooldown is active', async () => {
     const { svc } = buildService();
     svc.setInvitationCooldown(