feat(image-editor): wire Marquee + Burn + Rotate View

[lyfuci]

Summary

Three more PS-staple tools moved from stubs to functional. Bundled together because they're independent additions — no overlap in concerns or shared files beyond the usual i18n / palette / options-bar plumbing.

Marquee (M)

Real rectangular selection. Drag to define; selection persists in
`EditorState.selection` (history-tracked + .json round-trip); shown as
a static marching-ants outline (white dashes over a black halo for
legibility on any background). Cmd/Ctrl+A selects all,
Cmd/Ctrl+D deselects.

• New `marquee-drawing` interaction kind in `Canvas.tsx`.
• Selection lives in original-image preview-pixel space; parent shifts
  cropped-canvas coords back by the active crop origin before storing.
• `render.ts` gains a `liveCanvas` flag (true on live preview, false on
  export) — gates marching-ants chrome so it never bakes into pixels.
• `OptionsBar` marquee variant: hint text + "Deselect" button when a
  selection is active.
• `serialize.ts` adds `selection` to the parsed state.

No tools yet act on the selection — that's a follow-up PR per tool
(bucket / brush / fill within selection, etc.). This PR establishes
the selection state + UI; downstream wiring is straightforward.

Burn

Mirror of Dodge (#42). New `'burn'` in the `Tool` union; the dodge
branch now handles both (white+`lighter` vs. black+`multiply`).
Palette gets a Moon icon next to the dodge Sun. Layer-list distinguishes
burn strokes.

Rotate View (R)

View-only canvas rotation. New `viewRotation` state (0/90/180/270) in
ImageEditor; Workspace applies it as a CSS `rotate()` on the wrapper
transform. Pixels untouched. Toggled by R OR by clicking the
palette button (intercepted in `trySetTool` since rotateView has no
"tool mode" — every click just cycles the rotation).

`STUB_TOOLS` shrinks: `marquee` and `rotateView` removed.

Branched from `main` (independent).

Test plan

• Press M, drag — dashed marquee appears live; mouseup commits, marching-ants outline persists.
• Cmd+D — selection clears.
• Cmd+A — selection covers whole image.
• Save .json with selection active → reload → selection restored.
• Export PNG — marquee chrome NOT in the exported image.
• Crop, then marquee inside — selection lands in the right place; persists after crop is cleared.
• Click Burn palette button (Moon icon), drag — area visibly darkens; repeat strokes build up.
• Layer panel labels: dodge stroke vs. burn stroke distinct.
• Press R — workspace rotates 90°. Press 4× to return.
• Click Rotate View palette button — same cycle.

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