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>

scripts/install-hooks.js

@@ -127,6 +127,12 @@ const HOOKS_WITH_MATCHER = ["PreToolUse", "PostToolUse", "Stop", "SubagentStop",
 // tool-name matchers, hence the separate list.
 const HOOKS_WITHOUT_MATCHER = ["SessionStart", "SessionEnd", "UserPromptSubmit"];
 const HOOK_TYPES = [...HOOKS_WITH_MATCHER, ...HOOKS_WITHOUT_MATCHER];
+// Fired around EVERY tool call, and Claude Code waits for a synchronous hook
+// before it goes on — each one a Node start (0.1–0.2 s), so ~0.4 s added to
+// every tool call. The handler only reports (it prints nothing, decides
+// nothing), so these run in the background (`async`). The rarer events stay
+// synchronous so a turn's start and end still reach the dashboard in order.
+const ASYNC_HOOKS = new Set(["PreToolUse", "PostToolUse"]);
 
 function makeHookEntry(hookType) {
   const entry = {
@@ -134,6 +140,7 @@ function makeHookEntry(hookType) {
       {
         type: "command",
         command: `node "${HOOK_HANDLER}" ${hookType}`,
+        ...(ASYNC_HOOKS.has(hookType) && { async: true }),
       },
     ],
   };
@@ -247,4 +254,12 @@ if (require.main === module) {
 
 // isOurEntry is also used by scripts/plugin-bootstrap.js to strip hook entries
 // a previous checkout install left behind (they would double-count events).
-module.exports = { HOOK_TYPES, installHooks, isInsideContainer, isOurEntry, pluginProvidesHooks };
+module.exports = {
+  ASYNC_HOOKS,
+  HOOK_TYPES,
+  installHooks,
+  isInsideContainer,
+  isOurEntry,
+  makeHookEntry,
+  pluginProvidesHooks,
+};