Write thread events for taskless communication runs

recordThreadEvent used to drop the event whenever `envelope.taskId` was
null, so communication wakes produced nothing in the thread view even
while the agent actively replied to peers. Taskless runs now write into
a per-agent general thread (`ensureAgentCommunicationThread`), so the UI
surfaces peer conversations alongside task activity.

Peer-authored user turns inside the transcript used to be labelled with
the recipient's id — pi erases the sender once the message is projected.
A new `inboundCorrelations` map on `RuntimeBridge` pins each pi-message
timestamp to its source `agent_messages` row at injection time, so the
thread-event writer can recover the real author id and `senderKind` on
`message_end`. prepareRun projections (no `message_end` fires for
priorMessages) write their thread event directly as the projection lands
so they are not silently lost.

src/main/thread-integration/thread-helpers.ts

@@ -35,6 +35,42 @@ export function ensureTaskThread(db: AppDatabase, taskId: string, companyId: str
   });
 }
 
+export function findAgentCommunicationThread(db: AppDatabase, agentId: string, companyId: string) {
+  const existing = db.listThreads({
+    companyId,
+    type: "general" as ThreadType,
+    relatedEntityType: "agent",
+    relatedEntityId: agentId,
+    limit: 1,
+  });
+  return existing[0] ?? null;
+}
+
+/**
+ * Returns (or creates) the single "general" thread that accumulates an
+ * agent's taskless communication activity. Task runs already write into
+ * a task-scoped thread; taskless communication runs would otherwise drop
+ * their conversation events on the floor, leaving the thread view blank
+ * even while the agent actively replies to peers.
+ */
+export function ensureAgentCommunicationThread(
+  db: AppDatabase,
+  agentId: string,
+  companyId: string,
+  agentLabel: string,
+) {
+  const existing = findAgentCommunicationThread(db, agentId, companyId);
+  if (existing) return existing;
+
+  return db.createThread({
+    companyId,
+    title: `${agentLabel} · communication`,
+    type: "general" as ThreadType,
+    relatedEntityType: "agent",
+    relatedEntityId: agentId,
+  });
+}
+
 export function findApprovalThread(db: AppDatabase, approvalId: string, companyId: string) {
   const existing = db.listThreads({
     companyId,