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>

src/services/reddit-account-runtime-builder.ts

@@ -257,16 +257,15 @@ async function buildRuntime(
       undefined,
       undefined,
       mediaExchange,
+      // Read through to the live config object rather than snapshotting, so a
+      // dashboard configuration save applies to a running account without a
+      // restart. The service reads these on every inbound reply.
       {
-        offPlatformKill: accountConfig.conversations.offPlatformKill,
-        killOnSellerKeyword: accountConfig.conversations.killOnSellerKeyword,
+        get offPlatformKill() { return accountConfig.conversations.offPlatformKill; },
+        get killOnSellerKeyword() { return accountConfig.conversations.killOnSellerKeyword; },
         triage: conversationReadStateRepo,
         screener: aiClient,
-        screening: {
-          enabled: accountConfig.conversations.aiReplyScreening.enabled,
-          killConfidence: accountConfig.conversations.aiReplyScreening.killConfidence,
-          flagConfidence: accountConfig.conversations.aiReplyScreening.flagConfidence,
-        },
+        get screening() { return accountConfig.conversations.aiReplyScreening; },
       },
     );