Replace hand-rolled pointer-resize logic (TaskContextPanel's 3-way vertical
split, SessionChatWindow's rail, ChatThread's message/input split) with
svelte-splitpanes, themed onto the app's existing border/primary tokens.
- TaskContextPanel: Scope/Plan/Event-log sections collapse to a fixed header
height and restore their last size on reopen.
- ChatThread: input area is now a separate resizable pane, clamped to a
measured one-line minimum and a 45% max, instead of a fixed max-h textarea.
- Send button restyled to sit inside the input's corner (Claude-style),
swapping the up-arrow for a corner-down-left return icon.
- Adds a $app/environment shim + optimizeDeps exclude, since
svelte-splitpanes assumes SvelteKit and this is a plain Vite app.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
dtoro
58a11ca872