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/lib/pane-mode.js

@@ -57,13 +57,18 @@ function readMode(runId) {
 const fail = (code, message) => Object.assign(new Error(message), { code });
 const sleep = (ms) => new Promise((r) => setTimeout(r, ms));
 
+// Between two reads of the pane. Each read is a SYNCHRONOUS capture-pane
+// (through sudo for a member's pane) that holds up every other request and
+// socket while it runs, so a mode change polls gently rather than 20×/s.
+const POLL_MS = 150;
+
 // The mode once it differs from `from` — or what the pane shows at the deadline.
 async function nextMode(runId, from, waitMs) {
   const until = Date.now() + waitMs;
   for (;;) {
     const now = readMode(runId);
     if ((now && now !== from) || Date.now() >= until) return now;
-    await sleep(50);
+    await sleep(POLL_MS);
   }
 }