0.17.0: split SVG layer into per-path layers

Right-click an SVG-backed layer to split it into one layer per
top-level drawable. Each part keeps the original stage position
and ends up as a same-size standalone SVG.

Also: delete confirm now floats above the welcome dialog (topmost
z-index + scoped ESC/Tab via modal stack) and autofocuses its
primary button so Enter triggers confirm instead of bubbling back
to the underlying row.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/i18n/messages.ts

@@ -294,6 +294,7 @@ export const en = {
     separate: 'Separate Position and Rotation',
     rotation: 'Rotation',
     position: 'Position',
+    splitSvg: 'Split SVG into paths',
     removeInstanceDialog: {
       title: 'Remove clip instance?',
       message: 'Remove "{name}" at {time}s from the timeline.',