Switch from delete+recreate to PUT in-place updates

- Removes flicker caused by delete+recreate pattern
- PUT updates modify post content in-place (smooth)
- Trade-off: Mattermost shows (edited) label, and PUT clears pin status
- Pin+PUT are incompatible in Mattermost API — every PUT clears is_pinned
- Fix pin API calls to use {} body instead of null
- Remove post-replaced event handler (no longer needed)

src/watcher-manager.js

@@ -240,6 +240,14 @@ async function startDaemon() {
         const initialText = buildInitialText(agentId, sessionKey);
         postId = await sharedStatusBox.createPost(channelId, initialText, rootPostId);
         logger.info({ sessionKey, postId, channelId }, 'Created status box');
+
+        // Auto-pin the status post so it's always visible
+        try {
+          await sharedStatusBox._apiCall('POST', '/api/v4/posts/' + postId + '/pin', {});
+          logger.debug({ sessionKey, postId }, 'Status post pinned');
+        } catch (pinErr) {
+          logger.warn({ sessionKey, err: pinErr }, 'Failed to pin status post');
+        }
       } catch (err) {
         logger.error({ sessionKey, err }, 'Failed to create status post');
         globalMetrics.lastError = err.message;
@@ -282,18 +290,6 @@ async function startDaemon() {
     logger.debug({ sessionKey }, 'Session removed from sessions.json');
   });
 
-  // ---- Post Replaced (delete+recreate) ----
-  sharedStatusBox.on('post-replaced', (oldPostId, newPostId) => {
-    // Update activeBoxes to point to new post ID
-    for (var entry of activeBoxes.entries()) {
-      if (entry[1].postId === oldPostId) {
-        entry[1].postId = newPostId;
-        logger.debug({ sessionKey: entry[0], oldPostId, newPostId }, 'Post replaced (delete+recreate)');
-        break;
-      }
-    }
-  });
-
   // ---- Session Update (from watcher) ----
   watcher.on('session-update', (sessionKey, state) => {
     const box = activeBoxes.get(sessionKey);
@@ -345,7 +341,7 @@ async function startDaemon() {
 
     // Unpin the status post when session is done
     try {
-      await sharedStatusBox._apiCall('POST', `/api/v4/posts/${box.postId}/unpin`, null);
+      await sharedStatusBox._apiCall('POST', `/api/v4/posts/${box.postId}/unpin`, {});
       logger.debug({ sessionKey, postId: box.postId }, 'Status post unpinned');
     } catch (unpinErr) {
       logger.warn({ sessionKey, err: unpinErr }, 'Failed to unpin status post');