Feat v0.6.11 CSS deduplication (#46)

Retire old primitives.css button/toast/popup-menu/dropdown/tabs systems.
sw-primitives.css is now the single source of truth.

- Migrate 29 files from .btn-* to .sw-btn .sw-btn--{variant} .sw-btn--{size}
- Delete old toast, popup-menu, dropdown, tabs CSS (no JS references)
- Resolve .sw-dropdown and .sw-tabs class name collisions
- Resolve .settings-section duplicate (modals.css removed, surfaces.css authoritative)
- Add .sw-btn--success variant, --bg-active CSS variable
- Fix sdk-test-runner wrong variable names, icd-test-runner button fallbacks
- Add scripts/audit-css-collisions.sh

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/audit-css-collisions.sh

@@ -0,0 +1,74 @@
+#!/usr/bin/env bash
+# audit-css-collisions.sh — Find duplicate class selectors across kernel CSS files
+# Outputs a JSON collision report to stdout.
+# Usage: bash scripts/audit-css-collisions.sh [css-dir]
+
+set -euo pipefail
+CSS_DIR="${1:-src/css}"
+
+# Extract class selectors from CSS files and track their file + line
+declare -A SEEN      # selector -> "file:line file:line ..."
+
+for f in "$CSS_DIR"/*.css; do
+  [ -f "$f" ] || continue
+  lineno=0
+  while IFS= read -r line; do
+    lineno=$((lineno + 1))
+    # Extract class selectors (e.g. .foo-bar, .foo__bar--baz)
+    # Skip lines that are comments, inside @keyframes, or @media queries
+    [[ "$line" =~ ^[[:space:]]*/\* ]] && continue
+    [[ "$line" =~ ^[[:space:]]*@keyframes ]] && continue
+
+    # Match class selectors at the start of a rule
+    while [[ "$line" =~ \.([a-zA-Z_][a-zA-Z0-9_-]*) ]]; do
+      cls=".${BASH_REMATCH[1]}"
+      entry="$(basename "$f"):$lineno"
+      if [ -n "${SEEN[$cls]:-}" ]; then
+        SEEN[$cls]="${SEEN[$cls]} $entry"
+      else
+        SEEN[$cls]="$entry"
+      fi
+      # Remove the matched portion to find more classes on the same line
+      line="${line#*${BASH_REMATCH[0]}}"
+    done
+  done < "$f"
+done
+
+# Build JSON: only emit selectors defined in more than one file
+echo "["
+first=true
+for cls in "${!SEEN[@]}"; do
+  locations="${SEEN[$cls]}"
+  # Get unique files
+  files=()
+  for loc in $locations; do
+    file="${loc%%:*}"
+    found=false
+    for f in "${files[@]:-}"; do
+      [ "$f" = "$file" ] && found=true && break
+    done
+    $found || files+=("$file")
+  done
+
+  # Only report if defined in 2+ different files
+  [ ${#files[@]} -lt 2 ] && continue
+
+  if $first; then first=false; else echo ","; fi
+
+  # Build locations array
+  locs_json=""
+  for loc in $locations; do
+    [ -n "$locs_json" ] && locs_json="$locs_json, "
+    locs_json="$locs_json\"$loc\""
+  done
+
+  files_json=""
+  for f in "${files[@]}"; do
+    [ -n "$files_json" ] && files_json="$files_json, "
+    files_json="$files_json\"$f\""
+  done
+
+  printf '  {"selector": "%s", "files": [%s], "locations": [%s]}' "$cls" "$files_json" "$locs_json"
+done
+echo ""
+echo "]"