feat(minimize): collapse the chat to a floating mascot with edge-aware restore

[quiet-node]

Overview

Adds minimize / restore to the overlay. Instead of dismissing the chat (which cancels generation and starts a fresh session), the user can park an in-progress conversation as a small floating mascot icon and bring it back later, with the response still streaming in the background. The transition is one connected morph: the chat dissolves into the mascot on collapse and blooms back on restore, running as a GPU transform while the native window only snap-resizes at the endpoints.

Highlights

• Park, don't lose. Minimize keeps the conversation and its in-flight stream alive; a jewel dot on the mascot lights when a reply finishes while parked.
• Edge-aware restore. The chat unfolds into open screen space, flipping its anchor and clamping to the monitor so it never opens off-screen, wherever the icon was dragged.
• Hotkey-aware. While minimized, double-tap-Control restores instead of starting fresh, and tray/close paths leave the parked chat intact.

How it works

A morphPhase state machine (idle → collapsing → minimized → expanding → idle) in App.tsx drives Framer Motion; positioning math lives in a pure morphGeometry.ts. An OVERLAY_MINIMIZED atomic in lib.rs routes activations to a restore while parked and is kept in sync with the React phase at every transition.

Testing

bun run test:all:coverage and bun run validate-build pass clean. Frontend is at 100% coverage (lines/branches/functions/statements); new suites cover the full lifecycle, edge-aware geometry, the unseen indicator, and focus wiring.

Note: lib.rs is excluded from the Rust coverage gate, so its &AppHandle window/visibility functions are exercised via the frontend integration tests. One unreachable-in-jsdom guard carries a justified /* v8 ignore */.