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/run/PaneChat.tsx

@@ -467,6 +467,19 @@ export const PaneChat = memo(function PaneChat({
     []
   );
 
+  // Stable, so typing in the prompt box does not re-render the conversation
+  // (ConversationView is memoized).
+  const openTerminal = useCallback(() => showTerminal(runId, sessionId), [runId, sessionId]);
+  const openFile = useCallback(
+    (path: string) => {
+      // The workspace's Changes panel when the file is in its folder;
+      // else this view's own preview.
+      if (laneId !== null && openInChanges(laneId, cwd, path)) return;
+      setPreview(path);
+    },
+    [laneId, cwd]
+  );
+
   // Before the session starts the CLI may be asking in the terminal (trust
   // this folder? with "No, exit" preselected): an Enter from here answers it.
   // Asked, not refused: whether the session row appears right after the
@@ -515,15 +528,10 @@ export const PaneChat = memo(function PaneChat({
             follow={follow}
             waiting={asking}
             stopped={stops}
-            onOpenTerminal={() => showTerminal(runId, sessionId)}
+            onOpenTerminal={openTerminal}
             onContext={onContext}
             onNotStarted={setNotStarted}
-            onOpenFile={(path) => {
-              // The workspace's Changes panel when the file is in its folder;
-              // else this view's own preview.
-              if (laneId !== null && openInChanges(laneId, cwd, path)) return;
-              setPreview(path);
-            }}
+            onOpenFile={openFile}
           />
           {!outlineOpen && !preview && (
             <button