feat: make the conversation kill controls settable from the dashboard

The `conversations` section was only reachable by editing config.yaml, which
production ignores: config is database-backed and the YAML is imported once,
when the database has not yet been seeded. `AdvancedConfigSchema` is also a
strict object, so a PUT carrying the section was rejected outright.

- Add `conversations` to the advanced config schema and payload, so it appears
  in the dashboard's advanced JSON editor and survives a save.
- Apply the edited section field by field rather than replacing the objects,
  and read the flags through to the live config from the account runtime, so a
  save applies to a running account without a restart.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/conversation-automation.test.ts

@@ -327,6 +327,28 @@ describe('conversation automation', () => {
     expect(chat.sendChatMessage).toHaveBeenCalledOnce();
   });
 
+  it('re-reads the screening options on every reply so a config change applies without a restart', async () => {
+    const screener = {
+      screenConversationReply: vi.fn().mockResolvedValue({
+        classification: 'seller', confidence: 0.95, evidence: 'selling',
+      }),
+    };
+    const screening = { enabled: false, killConfidence: 0.8, flagConfidence: 0.6 };
+    const { service, getSaved } = harness([], [], 0, { mode: 'r4r', maxAutomatedTurns: 5 }, undefined, undefined, {
+      screener,
+      screening,
+    });
+
+    expect((await service.processConversation(incoming(1)))?.kind).toBe('sent');
+    expect(screener.screenConversationReply).not.toHaveBeenCalled();
+
+    screening.enabled = true;
+
+    expect((await service.processConversation(incoming(2)))?.kind).toBe('killed');
+    expect(screener.screenConversationReply).toHaveBeenCalledOnce();
+    expect(getSaved()?.automation.status).toBe('killed');
+  });
+
   it('does not call the screener at all when screening is disabled', async () => {
     const screener = { screenConversationReply: vi.fn() };
     const { service } = harness([], [], 0, undefined, undefined, undefined, {