Unify message read state on agent_message_reads

listAgentInboxUnread's direct-channel branch filtered on
agent_messages.read_at, a column no code path in the repo ever writes.
Every DM was therefore reported unread on every wake — the standup kept
re-surfacing the same message, agents either looped on duplicate replies
or devolved into posting status comments instead of real replies.

Route every channel through agent_message_reads. The legacy read_at
column stays in the schema as a wire-shape placeholder but is explicitly
documented as unused; every surface that returns readAt already derives
it from the receipts table.

Also delete the wake-reason instruction that taught agents to post a
status comment when nothing needs attention — that line was the direct
source of heartbeat-noise comments cluttering the activity feed.

src/main/database/messages.ts

@@ -264,10 +264,13 @@ export function buildMessageMethods(
      * visibility rules as listAgentMessages (direct/company/incident always,
      * department when agent belongs, project when assigned/lead).
      *
-     * "Unread" means:
-     *  - Direct messages to this agent: `agent_messages.read_at IS NULL`.
-     *  - Channel messages: no matching row in `agent_message_reads` for
-     *    (message_id, agent_id).
+     * "Unread" is defined uniformly across every channel: no row in
+     * `agent_message_reads` for (message_id, agent_id). The legacy
+     * `agent_messages.read_at` column is never written anywhere in the
+     * codebase and must not be used as a read signal — it only appears in
+     * SELECT lists for wire-shape compatibility and is overwritten from the
+     * read-receipts table by every caller that surfaces `readAt` to agents
+     * or the renderer.
      *
      * Messages where `from_agent_id = agentId` are excluded (agents don't
      * inject their own sent messages back into their transcript).
@@ -331,12 +334,7 @@ export function buildMessageMethods(
         ).map((row) => row.messageId),
       );
 
-      return rows.filter((message) => {
-        if (message.channel === "direct" && message.toAgentId === agentId) {
-          return !message.readAt;
-        }
-        return !readIds.has(message.id);
-      });
+      return rows.filter((message) => !readIds.has(message.id));
     },
 
   };

src/main/prompt-builder/wake-reasons/en.ts

@@ -28,7 +28,7 @@ export const WAKE_REASONS: Record<WakeReason, WakeReasonEntry> = {
       "Call GET /api/agents/me/standup to get your full briefing",
       "Review all your assigned tasks and their statuses",
       "Take action on the most important item: reviews > unblocking > new work",
-      "If nothing needs attention, post a brief status update on your current task",
+      "If nothing actionable is in your briefing, return control without posting a status comment — activity noise is worse than silence.",
     ],
   },
   manual: {