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/__tests__/install-hooks.test.js

@@ -142,6 +142,19 @@ describe("install-hooks host-only guard (#193)", () => {
   });
 });
 
+describe("async hooks", () => {
+  it("runs only the per-tool-call hooks in the background, in settings and the plugin alike", () => {
+    const { makeHookEntry, ASYNC_HOOKS } = require("../../scripts/install-hooks");
+    const plugin = require("../../.claude-plugin/plugin.json");
+    assert.deepEqual([...ASYNC_HOOKS].sort(), ["PostToolUse", "PreToolUse"]);
+    for (const type of HOOK_TYPES) {
+      const want = ASYNC_HOOKS.has(type) ? true : undefined;
+      assert.equal(makeHookEntry(type).hooks[0].async, want, `settings ${type}`);
+      assert.equal(plugin.hooks[type][0].hooks[0].async, want, `plugin ${type}`);
+    }
+  });
+});
+
 describe("HOOK_TYPES", () => {
   it("is the event list the plugin ships, so the hook status checks every one", () => {
     const exported = require("../../scripts/install-hooks").HOOK_TYPES;