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/BannerStripView.swift

@@ -40,6 +40,15 @@ public struct BannerStripView: View {
     /// How many rows show before the disclosure takes over.
     private static let collapseThreshold = 3
 
+    /// The strip's own rhythm, font-derived like everything else the app lays out
+    /// (`BoardMetrics`, 10-accessibility.md ▸ Text scaling: "no fixed point sizes"). It matters here
+    /// because a banner row *wraps* rather than truncating — the cause tail is the half that says
+    /// what to do — so a fixed inset around growing text crowds fast.
+    @MainActor static var rowHorizontalPadding: CGFloat { BoardMetrics.em(0.9, bodyPointSize: pointSize) }
+    @MainActor static var rowVerticalPadding: CGFloat { BoardMetrics.em(0.6, bodyPointSize: pointSize) }
+    @MainActor static var rowSpacing: CGFloat { BoardMetrics.em(0.6, bodyPointSize: pointSize) }
+    @MainActor private static var pointSize: CGFloat { BoardMetrics.bodyPointSize }
+
     @State private var isExpanded = false
 
     public init(rows: [BannerRow], onDismiss: @escaping (UUID) -> Void) {
@@ -101,15 +110,15 @@ public struct BannerStripView: View {
         Button {
             isExpanded.toggle()
         } label: {
-            HStack(spacing: 6) {
+            HStack(spacing: BannerStripView.rowSpacing) {
                 Image(systemName: isExpanded ? "chevron.up" : "chevron.down")
                     .imageScale(.small)
                 Text(isExpanded ? "Show fewer" : "+\(hiddenCount) more")
                 Spacer(minLength: 0)
             }
             .font(.callout)
-            .padding(.horizontal, 12)
-            .padding(.vertical, 6)
+            .padding(.horizontal, BannerStripView.rowHorizontalPadding)
+            .padding(.vertical, BannerStripView.rowSpacing)
             .contentShape(Rectangle())
         }
         .buttonStyle(.plain)
@@ -127,7 +136,7 @@ private struct BannerRowView: View {
     let onDismiss: (UUID) -> Void
 
     var body: some View {
-        HStack(alignment: .firstTextBaseline, spacing: 8) {
+        HStack(alignment: .firstTextBaseline, spacing: BannerStripView.rowVerticalPadding) {
             leading
 
             Text(row.headline)
@@ -139,8 +148,8 @@ private struct BannerRowView: View {
 
             trailingControls
         }
-        .padding(.horizontal, 12)
-        .padding(.vertical, 8)
+        .padding(.horizontal, BannerStripView.rowHorizontalPadding)
+        .padding(.vertical, BannerStripView.rowVerticalPadding)
         .frame(maxWidth: .infinity, alignment: .leading)
         .background(row.tone.fill)
         // One element per row, tone included: a VoiceOver user must hear *that* this is an error