The composer had two separate mode buttons (plan + panel). Fold them into a
single #planModeBtn that cycles through every operating mode in one place:
Off -> Plan -> Fusion -> MoA -> Off. Cleaner UI, one affordance instead of two.
Plan stays transient (reset on session switch, never persisted) while
Fusion/MoA persist to the session via apiUpdateSession({multiModelMode}) and
are read server-side from ctx.MultiModelMode. The compat var _planModeActive
is kept in sync (true iff mode === 'plan') so sendMessage and modals.js read
it unchanged. No text label — icon + tint only.
- index.html: drop the separate panel button, reuse #planModeBtn
- chat.css: unified states (plan/fusion/moa tints) on #planModeBtn
- chat.js: cycleCompositeMode / initCompositeMode / _renderCompositeBtn
replace the split plan/panel functions
- chat-page.js: single wiring block, init from session.multiModelMode
- ARCHITECTURE_QUICK.md: document the unified toggle
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
