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/server/install-system.sh

@@ -156,8 +156,11 @@ if [ -f "$MANAGED" ] && ! { [ -f "$MANAGED_MARK" ] && sha256sum -c --status "$MA
 else
   "$NODE" -e '
     const ev = ["PreToolUse","PostToolUse","Stop","SubagentStop","Notification","SessionStart","SessionEnd","UserPromptSubmit"];
+    // Per-tool-call hooks run in the background (async): a synchronous one
+    // makes Claude Code wait a Node start (0.1-0.2 s) before and after every call.
     const hook = (e) => [{ ...(["PreToolUse","PostToolUse"].includes(e) ? { matcher: "*" } : {}),
-      hooks: [{ type: "command", command: `/opt/agenthub/libexec/member-hook ${e}`, timeout: 5 }] }];
+      hooks: [{ type: "command", command: `/opt/agenthub/libexec/member-hook ${e}`, timeout: 5,
+        ...(["PreToolUse","PostToolUse"].includes(e) ? { async: true } : {}) }] }];
     process.stdout.write(JSON.stringify({ hooks: Object.fromEntries(ev.map((e) => [e, hook(e)])) }, null, 2) + "\n");
   ' >"$MANAGED"
   chmod 0644 "$MANAGED"