fix(messages): company channel fans out to every active agent

"Company" channel fell through to `listTopLevelAgentIds`, so a
broadcast on the most ambient-sounding channel in the product only
reached agents with `reports_to IS NULL`. The label said company;
the semantics said board-only. The rest of the org never knew a
message existed.

Add `listCompanyBroadcastAgentIds` — returns every non-terminated,
non-paused, non-pending agent for the company — and wire it through
the `company` case in `resolveMessageWakeTargets`. Board-only
fan-outs are still reachable: the `incident` channel keeps the
broader pingable set (paused-by-budget included) and direct DMs to
top-level agents work as before.

The prompt doc catches up to the runtime: company is explicitly
framed as all-hands, with board-only guidance redirected to DMs or
incidents. The message-dispatch unit test asserts the new fan-out.

tests/unit/message-dispatch.test.ts

@@ -125,7 +125,7 @@ function createScaffold(db: AppDatabase) {
 }
 
 describe("message dispatch", () => {
-  it("wakes top-level active agents for company messages and active agents for incident messages", async () => {
+  it("wakes every active agent for company channel broadcasts (Slack-style all-hands)", async () => {
     const profileDir = await createTempDir("agentcompany-message-dispatch-");
     const db = new AppDatabase(profileDir);
     db.init();
@@ -141,12 +141,12 @@ describe("message dispatch", () => {
       fromAgentId: HUMAN_SENDER_ID,
       fromHumanUser: true,
       channel: "company",
-      body: "Board broadcast",
+      body: "All-hands broadcast",
     });
 
     expect(companyResult.ok).toBe(true);
     if (!companyResult.ok) throw new Error("Expected company message dispatch to succeed.");
-    expect(companyResult.data.wakeTargets).toEqual([ceoId]);
+    expect(new Set(companyResult.data.wakeTargets)).toEqual(new Set([ceoId, ctoId, cmoId]));
 
     const incidentResult = dispatchAgentMessage({
       db,