feat(ui): floating widget windows (shell capability), enable for Image Map

[lstein]

Summary

PR 6 of the Image Map stack. Adds a generic floating-window layer to the workbench shell — any widget can opt in via manifest.allowFloating; the Image Map is the first user.

• State: Project.floatingWidgets maps instance ids to geometry, mode (windowed/maximized/shaded), z-order, and the region to dock back into. Additive + optional, so persisted projects hydrate unchanged; the field round-trips through project persistence and is captured/restored with widgetRegions in undo snapshots (they are one placement fact).
• Reducer actions: floatWidget (detaches from its region, repairs the active instance), dockFloatingWidget, setFloatingWidgetGeometry (min-size clamped), setFloatingWidgetMode, focusFloatingWidget. Invariant: an instance never renders docked and floating at once — placing a floating instance into a region implicitly docks it, and applying a layout preset docks all floating widgets.
• Window chrome: fixed-position Chakra window with title-bar drag and corner resize (raw-pointer commit-on-release, main button only), shade/maximize/dock buttons, double-click-to-shade (button-safe), and the standard widget renderer (bare) as its body. CSS clamp() keeps a grabbable sliver on-screen even for geometry persisted on a larger display. z-index derives from stacking rank, not the persisted monotonic counter, so long-lived projects can never climb past the UI library's layer tokens.
• "Float Window" lives in the shared widget actions menu, gated on the manifest flag.

An adversarial review of this diff was run; all confirmed findings are fixed with regression tests: preset-apply/undo double-render and widget-loss holes, off-screen stranding, z-token decay, double-click-on-button shading, non-main-button drags, plus the lint failures the review caught (my earlier lint invocation masked a failing format step — now verified by exit code).

Known accepted gaps (documented for reviewers): floating bodies don't participate in focus-region/hotkey attribution (irrelevant for Image Map, which registers no hotkeys — flagged for future floatable widgets); mid-drag unmount leaves window listeners until the next global pointerup (self-healing).

Testing

16 reducer/helper tests: float/dock round-trips, active-instance repair, geometry clamps, mode/no-op semantics, z-rank raising, preset-docking, undo consistency (widget is exactly one of docked/floating), viewport clamp math. Full suite: 885+ tests, pnpm lint + pnpm build pass.

🤖 Generated with Claude Code