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/DragShadow.swift

@@ -14,21 +14,32 @@ import SwiftUI
 /// target stays live beneath them"), and a shadow that swallowed the release would strand the drop.
 struct DragShadow: View {
 
-    /// Matched to the surface it stands in for — a lane's plate is 10, a card's is 8.
-    var cornerRadius: CGFloat = 10
+    /// Matched to the surface it stands in for — the lane's plate radius or the card's, both
+    /// font-derived (`BoardMetrics`) and both supplied by the caller, which is the one that knows
+    /// which surface this shadow is standing in for.
+    let cornerRadius: CGFloat
 
     /// A drop proposal (dashed) or a resting footprint (plain).
     var dashed: Bool = true
 
+    /// Increase Contrast and Reduce Transparency, for the outline and the fill below
+    /// (10-accessibility.md; `Accommodations`). A shadow's whole job is to say "here", and both
+    /// halves of how it says so are alpha-based by default.
+    @Environment(\.colorSchemeContrast) private var contrast
+    @Environment(\.accessibilityReduceTransparency) private var reduceTransparency
+
     var body: some View {
         RoundedRectangle(cornerRadius: cornerRadius)
-            .fill(.quaternary.opacity(0.5))
+            .fill(Accommodations.dragShadowWash(reduceTransparency: reduceTransparency).style)
             .overlay {
                 if dashed {
                     RoundedRectangle(cornerRadius: cornerRadius)
                         .strokeBorder(
-                            Color.accentColor.opacity(0.55),
-                            style: StrokeStyle(lineWidth: 1.5, dash: [6])
+                            Color.accentColor.opacity(Accommodations.accentOpacity(0.55, contrast: contrast)),
+                            style: StrokeStyle(
+                                lineWidth: Accommodations.borderWidth(1.5, contrast: contrast),
+                                dash: [6]
+                            )
                         )
                 }
             }
@@ -46,16 +57,24 @@ struct DragCountBadge: View {
 
     let count: Int
 
+    /// The badge is a disc around a numeral, so every figure in it follows the numeral's font
+    /// (`BoardMetrics`, 10-accessibility.md's full-relative-scaling rule) — at the standard body size
+    /// they are the 6, 3 and 10 points it has always drawn.
+    private var pointSize: CGFloat { BoardMetrics.bodyPointSize }
+
     var body: some View {
         if count > 1 {
             Text("\(count)")
                 .font(.caption2.bold())
                 .monospacedDigit()
                 .foregroundStyle(.white)
-                .padding(.horizontal, 6)
-                .padding(.vertical, 3)
+                .padding(.horizontal, BoardMetrics.em(0.45, bodyPointSize: pointSize))
+                .padding(.vertical, BoardMetrics.em(0.25, bodyPointSize: pointSize))
                 .background(Circle().fill(Color.accentColor))
-                .offset(x: 10, y: -10)
+                .offset(
+                    x: BoardMetrics.em(0.75, bodyPointSize: pointSize),
+                    y: -BoardMetrics.em(0.75, bodyPointSize: pointSize)
+                )
         }
     }
 }