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>

client/src/components/Sagi/PetSprite.tsx

@@ -58,6 +58,8 @@ const ROW: Record<Mood, number> = {
 /** What the user is doing to the pet, which outranks its mood. */
 export type PetAction = "run-left" | "run-right" | "wave";
 const ACTION_ROW: Record<PetAction, number> = { "run-right": 1, "run-left": 2, wave: 3 };
+/** Loops of a row before the sprite rests on its first frame. */
+const SPRITE_LOOPS = 4;
 
 export function PetSprite({
   id,
@@ -95,13 +97,17 @@ export function PetSprite({
     const own = play(row, sleeping ? SLEEP_SLOWDOWN : 1);
     let list = MOMENTS.has(row) ? [...own, ...own, ...own] : own;
     let i = 0;
+    let loops = 0;
     let timer = 0;
-    // `i` always indexes `list`: it wraps at its end.
+    // `i` always indexes `list`: it wraps at its end. A few loops, then the
+    // first frame rests — a sprite that never stops re-paints the page several
+    // times a second for as long as it is open; a new mood or action plays again.
     const tick = () => {
       timer = window.setTimeout(() => {
         if (++i === list.length) {
           i = 0;
           if (MOMENTS.has(row)) list = play(0);
+          if (++loops >= SPRITE_LOOPS) return setCell(list[0]!);
         }
         setCell(list[i]!);
         tick();