Implement visual accommodations and Full Keyboard Access

Full relative text scaling per DESIGN/10: BoardMetrics is the board
strip's geometry as a pure function of the body point size
(CardWindowMetrics' twin) — lane plate/header/band, card
corner/stripe/padding, masonry spacing, the drop model's nominal card
height, resize-handle geometry, trash hatch pitch, and both window
floors all derive from an em; CardFaceMetrics folded in. The two fixed
font sizes (welcome brand/glyph) went relative; the toolbar search
field is 17 ems like the transient bar's. The no-horizontal-scroll
invariant is pinned by test at six text sizes by twelve lane counts.

Accommodations is Motion's sibling for the visual settings: Increase
Contrast adds a flat point to strokes (monotone, hierarchy-preserving),
gives borderless card/lane plates a resting separator hairline, and
takes faded accents to full alpha; Reduce Transparency turns the
transient search bar's glass solid and does the same for the alpha
washes that composite over a user-chosen board background (trash plate,
hatched header, drag shadow). Reduce Motion audited — every animated
surface already routes through Motion with a reduced variant; no gaps.

Full Keyboard Access: the template chooser's tiles were pointer-only —
now focusable, arrow-navigable (clamped, StyleWellGrid's rule), Space
picks, Return stays the sheet's default action, focus names the
selection one-way. The board's single tab stop shows its focus ring
under FKA (focusEffectDisabled inverts). Style editor verified already
conformant. Edge accents verified text-free; trash hatch pitch now
font-derived so it still reads as hatching at large text.

1549 unit tests green, both schemes build.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

Kanban/UI/Board/BoardInfoPopover.swift

@@ -138,8 +138,12 @@ struct BoardInfoView: View {
     private let hasGitDirectory: Bool
 
     /// The style editor brings its own padding, so the sections around it carry the same number by
-    /// hand instead of an outer padding that would double up on it.
-    private let inset: CGFloat = 14
+    /// hand instead of an outer padding that would double up on it — **the editor's own figure**
+    /// (`StyleEditorLayout.sectionSpacing`), which is font-derived, so the popover's chrome scales
+    /// with the grids inside it (10-accessibility.md's full-relative-scaling rule).
+    private var inset: CGFloat {
+        StyleEditorLayout.sectionSpacing(bodyPointSize: CardWindowMetrics.bodyPointSize)
+    }
 
     init(store: BoardStore, recents: StyleRecents) {
         self.store = store
@@ -178,7 +182,10 @@ struct BoardInfoView: View {
                     .padding(inset)
             }
         }
-        .frame(width: 268)
+        // The style editor's popover width, taken from the editor rather than restated: the embed
+        // below must lay out here exactly as it does at its other two anchors, and that number is
+        // now font-derived.
+        .frame(width: StyleEditorLayout.popover(bodyPointSize: CardWindowMetrics.bodyPointSize).width)
     }
 
     /// The section titles, matching the style editor's own headers so the popover reads as one