Adds a floating popover above the chat input showing current
context-window usage. Modeled on Paseo's tracker.
- New hook useChatContextStats(chatId, messages) finds the latest
assistant message in the chat with both ctx_used and ctx_max set,
computes percent, and returns null when data unavailable.
- New component ChatContextPopover renders a small card with the
"Context window" label, big percent, and "used / max tokens"
subline. Hidden when stats is null.
- Color thresholds: <60% muted, 60-85 amber, >85 destructive.
- Not a portal — absolutely positioned inside a new relative
wrapper around ChatInput in ChatPane.tsx, so it's pane-local
(multi-pane safe).
- Live updates via the existing messages-array dependency.
- No API / schema / WS changes.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
