)

Reported in #721: typing in the dashboard composer feels laggy on long
sessions. Root cause is that every keystroke commits to `input` state,
which forces ChatPanel to walk its entire vnode tree on each frame.

ChatMessage was already wrapped in memo (#560), so historical bubbles
short-circuit individually — but Preact still has to map() over every
message, evaluate the per-row `Boolean(streaming && streaming.id === m.id)`
discriminator, and diff each ChatMessage element. For a session with
100+ messages the per-keystroke work is enough to drop frames.

Move the message-list render into a `<ChatFeed>` sub-component and wrap
it in memo. With `messages` and `streaming` refs both stable while the
user is typing, memo bails the whole feed out — keystrokes no longer
touch the feed at all. SideRail and ChatStatusBar get the same
treatment so /overview poll churn and input edits don't repaint the
right-rail progress bars and statusbar.

Closes #721

… jobs (esengine#560)

Chrome's "Page not responding" dialog fires on the dashboard chat tab
once a session accumulates enough messages. Repro condition: long
streaming turn or several concurrent jobs broadcasting at once.

Two cooperating bugs on the chat feed's hot path:

1. Every assistant_delta event hit setState synchronously. The model
   streams ~20 deltas/sec; each one re-rendered ChatPanel, which
   .map'd over every historical ChatMessage with no memoization, so
   each one re-ran marked.parse + (for tool messages) hljs syntax
   highlight on UNCHANGED content. Long sessions = N grows = main
   thread starves.
2. The `streaming` prop fed to historical ChatMessage flipped between
   `null` (no streaming) and `false` (streaming-but-not-this-message)
   across turns, so even with memo, `null !== false` would force
   every historical message to re-render every time streaming
   started or stopped.

Fix:

- Wrap ChatMessage in `memo` from preact/compat so historical messages
  with stable `msg` refs short-circuit re-renders.
- Cast the per-row streaming prop to a boolean so historical
  messages get a stable `false` and memo's shallow compare actually
  bails out across streaming-on/off transitions.
- Coalesce assistant_delta into a single rAF-batched setStreaming.
  Multiple deltas in the same frame collapse into one state commit;
  the streaming bubble's re-render rate is capped at the display
  refresh rate. assistant_final + SSE reconnect + unmount each
  cancel the pending flush so the buffer can't leak across turns.

Closes esengine#551

…sengine#729)

Reported in esengine#721: typing in the dashboard composer feels laggy on long
sessions. Root cause is that every keystroke commits to `input` state,
which forces ChatPanel to walk its entire vnode tree on each frame.

ChatMessage was already wrapped in memo (esengine#560), so historical bubbles
short-circuit individually — but Preact still has to map() over every
message, evaluate the per-row `Boolean(streaming && streaming.id === m.id)`
discriminator, and diff each ChatMessage element. For a session with
100+ messages the per-keystroke work is enough to drop frames.

Move the message-list render into a `<ChatFeed>` sub-component and wrap
it in memo. With `messages` and `streaming` refs both stable while the
user is typing, memo bails the whole feed out — keystrokes no longer
touch the feed at all. SideRail and ChatStatusBar get the same
treatment so /overview poll churn and input edits don't repaint the
right-rail progress bars and statusbar.

Closes esengine#721