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>

docs/SERVER-MODE.md

@@ -796,7 +796,9 @@ What a new machine still needs by hand after it:
    `PostToolUse` (both with `"matcher": "*"`), `Stop`, `SubagentStop`,
    `Notification`, `SessionStart`, `SessionEnd` and `UserPromptSubmit`, a
    `command` hook `/opt/agenthub/libexec/member-hook <Event>` with
-   `"timeout": 5`.
+   `"timeout": 5` — and `"async": true` on `PreToolUse` and `PostToolUse`, so
+   Claude Code does not wait a Node start before and after every tool call.
+   Re-running `install-system` rewrites a managed file it wrote itself.
 5. Any other daemon that must see every process (monitoring agents, for
    example) needs group `agenthub-proc`: `sudo usermod -aG agenthub-proc <it>`.
 6. A tool `agenthub server tools` reports as `ESHAREDLAYOUT` (a script in a