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/conversation/ConversationView.tsx

@@ -61,7 +61,7 @@
  *
  * ----------------------------------------------------------------------------- */
 
-import { useEffect, useState, useCallback, useMemo, useRef } from "react";
+import { memo, useEffect, useState, useCallback, useMemo, useRef } from "react";
 import { Loader2, ArrowDown, MessagesSquare, RefreshCw } from "lucide-react";
 import { api } from "../../lib/api";
 import { eventBus } from "../../lib/eventBus";
@@ -112,7 +112,7 @@ interface ConversationViewProps {
   onNotStarted?: (notStarted: boolean) => void;
 }
 
-export function ConversationView({
+function ConversationViewPane({
   sessionId,
   initialTranscriptId,
   fill = false,
@@ -646,3 +646,7 @@ export function ConversationView({
     </div>
   );
 }
+
+/** Memoized: a chat's prompt box lives in its parent (PaneChat), and every
+ *  keystroke there re-rendered the whole conversation. */
+export const ConversationView = memo(ConversationViewPane);

client/src/components/conversation/MessageList.tsx

@@ -633,7 +633,7 @@ const EditedFiles = memo(
     sameResults(n.blocks, p.toolResultMap, n.toolResultMap)
 );
 
-export function MessageList({
+function MessageListView({
   messages,
   loading,
   onOpenFile,
@@ -1550,3 +1550,6 @@ const MessageRow = memo(
   MessageRowView,
   (p, n) => p.msg === n.msg && sameResults(n.msg.content, p.toolResultMap, n.toolResultMap)
 );
+
+/** Memoized: its owner re-renders on scroll state and its parent's typing. */
+export const MessageList = memo(MessageListView);