fix(sw): refine property panel and Firefox range styles

- Property bar ends after its last field (content width, scrolls when longer)
- Remove Figma canvas layers from property tool and close SVGs
- Suppress header field hover while the field's own dropdown is open
- Gauge: Figma red fill pill, beige track, Figma thumb SVG; shared
  paint for WebKit and Gecko (::-moz-range-*) so Firefox matches Chrome
- Story buttons for gauge external value / disabled / read-only
- Browser checks: follow-up fixes, Chrome vs Firefox range, close button

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/sw/src/assets/property-tool-hover.svg

@@ -1,10 +1,6 @@
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-<rect width="29" height="28" fill="#F5F5F5"/>
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-<rect x="-19.5" y="-66.6328" width="68" height="160.387" rx="4.5" stroke="#9747FF" stroke-dasharray="10 5"/>
 <g id="Property 1=Variant2">
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