perf: rest animations, cheaper chat typing and server polls, async per-tool hooks

UI
- No animation runs forever: Sagi moods, the custom pet sprite, status dots
  (pulse-dot, pulse-slow, ping) and the chat shimmer play a few cycles and
  rest. An infinite animation kept the browser drawing 60 frames a second.
- useSagiBrain: frames that only move lastActivityAt by <1 s keep the old
  state; the 1 s tick re-renders only when the mood changes.
- ConversationView and MessageList are memoized and PaneChat passes stable
  callbacks: typing in the chat box no longer re-renders the conversation.
- The chat's 700 ms menu poll reads plain text first and scans the terminal
  cell by cell (reusing one cell) only when a row could be a menu cursor row.

Server
- GET /sessions/:id/transcript?after=N skips lines <= N before JSON.parse.
- GET /sessions/:id/outline is cached until the session's events change.
- broadcastLane uses the cached tmux.liveSessions(); tmux.hasSession answers
  "yes" from the fresh shared list instead of a synchronous spawn (50-150 ms
  per psmux call on Windows, blocking terminal echo).
- pane-mode polls every 150 ms; writeHourly writes only changed hour buckets.
- /api/metrics: agenthub_event_loop_delay_seconds{quantile}.

Hooks
- PreToolUse/PostToolUse run with "async": true (settings installer,
  plugin.json, S3 managed settings): Claude Code no longer waits a Node start
  before and after every tool call.

Committed with --no-verify at the owner's request: the pre-commit full server
suite fails on 9 tests that fail identically on 0c2f498 (lane-sync merge: no
git identity on this host; read-pool; resolveHost; codex-usage 1 ms flake).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/routes/sessions.js

@@ -469,11 +469,31 @@ function sessionOutline(sessionId) {
   };
 }
 
+// Each open chat polls its outline every few seconds, and building it parses
+// every tool event of the session: keep the last answer per session until its
+// events change (a new id, or fewer rows after a cleanup).
+const outlineStamp = db.prepare(
+  "SELECT MAX(id) AS max_id, COUNT(*) AS n FROM events WHERE session_id = ?"
+);
+const OUTLINE_CACHE_MAX = 100;
+const outlineCache = new Map();
+function cachedOutline(sessionId) {
+  const st = outlineStamp.get(sessionId);
+  const stamp = `${st.max_id}:${st.n}`;
+  const hit = outlineCache.get(sessionId);
+  if (hit && hit.stamp === stamp) return hit.body;
+  const body = sessionOutline(sessionId);
+  outlineCache.delete(sessionId);
+  outlineCache.set(sessionId, { stamp, body });
+  if (outlineCache.size > OUTLINE_CACHE_MAX) outlineCache.delete(outlineCache.keys().next().value);
+  return body;
+}
+
 router.get("/:id/outline", (req, res) => {
   if (!stmts.getSession.get(req.params.id)) {
     return res.status(404).json({ error: { code: "NOT_FOUND", message: "Session not found" } });
   }
-  res.json(sessionOutline(req.params.id));
+  res.json(cachedOutline(req.params.id));
 });
 
 // An image the session's own Read tool returned (`?path=`, exact), for the Chat
@@ -1165,10 +1185,13 @@ router.get("/:id/transcript", async (req, res) => {
     }
 
     if (afterLine !== null) {
-      // Incremental mode: skip lines until after afterLine, collect up to limit, then stop
-      let foundStart = false;
+      // Incremental mode: skip lines until after afterLine, collect up to limit, then stop.
+      // A line the client already has is skipped BEFORE it is parsed: every open
+      // chat tails its transcript every few seconds, and parsing the whole JSONL
+      // (MBs for a long session) each time was most of the server's steady CPU.
       for await (const line of rl) {
         lineNum++;
+        if (lineNum <= afterLine) continue;
         if (!line.trim()) continue;
         let entry;
         try {
@@ -1178,11 +1201,6 @@ router.get("/:id/transcript", async (req, res) => {
         }
         if (!renders(entry)) continue;
 
-        if (!foundStart) {
-          if (lineNum <= afterLine) continue;
-          foundStart = true;
-        }
-
         const message = isCodex ? codexMessage(entry, lineNum) : parseMessage(entry, lineNum);
         if (!message) continue;
         total++;