feat(sw): bold 9-slice footer tabs and viewer panel bottom edge

User-approved 2026-10-22 SW changes (CSS only, public API unchanged).
- Footer Model / Layout tab labels 700 in every state, letter-spacing -5%;
  the name-edit input keeps 400.
- Slanted Layout tab and Model tab draw their SVG assets as 9-slice
  border-images: 97px / 73px stay the minimum, the slant and corners keep
  their size and only the flat middle grows with a longer label (max 12em,
  then ellipsis, like the rounded tabs). Hover surfaces use a union mask of
  the same asset (no mask-border), so Chromium and Firefox match. The
  default width renders pixel-identical to the previous drawing; the 8px
  slant / Model joint is unchanged.
- Viewer panel body: the 7px bottom padding (inside the scrollport) becomes
  a 2px transparent bottom border, so scrolled rows stop 2px above the
  frame border instead of running into it. SWPopup keeps its 7px.
- AI docs: DESIGN_RULES, AI_USAGE, FOOTER, VIEWER updated.
- Tests: text-weight and footer-design-review expect the 700 labels and read
  the Model surface from the 9-slice ::before.

packages/sw/src/theme/sw-viewer.css

@@ -552,6 +552,10 @@ button.hm-sw-viewer-header__brand { text-align: left; }
 /* ---------- Panel (SWPopup frame + viewer window behavior) ---------- */
 .hm-sw-viewer-panel-backdrop { inset: 0; background: var(--hm-sw-viewer-panel-overlay); }
 .hm-sw-viewer-panel[data-collapsed] .hm-sw-property__body { display: none; }
+/* Bottom gutter outside the scrollport (2026-10-22, user-set 2px): the SWPopup body's 7px bottom padding is inside the
+   scroll area, so scrolled rows ran into it up to the frame border. A transparent border instead clips the list
+   2px above the frame border. */
+.hm-sw-viewer-panel .hm-sw-property__body { padding-bottom: 0; border-bottom: 2px solid transparent; }
 .hm-sw-viewer-panel[data-draggable] .hm-sw-property__titlebar { cursor: grab; touch-action: none; user-select: none; }
 .hm-sw-viewer-panel[data-dragging] .hm-sw-property__titlebar { cursor: grabbing; }
 /* Any width: the Figma title art keeps its 308px curve at the close button (right-aligned; at 314px this is exactly