feat(app): route every page with wouter

Replace the single-scroll showcase and its anchor/scrollIntoView
navigation with real routes: /, /patterns, /components/*, /foundations/*,
/docs/*, plus a 404 fallback.

- src/app/routes.tsx is the route table and the only source for paths,
  section headings, sidebar entries, breadcrumbs and the rail, so
  navigation cannot drift from the pages that exist
- src/pages/* holds one component per route; App.tsx is now the shell
  (topbar, sidebar, breadcrumbs, Switch, right rail, scroll-to-top)
- the active pattern moves into the URL (/patterns?pattern=table) and the
  sidebar/palette deep-link into it; SearchPalette results now carry a path
- Sidebar/RightRail render <Link> with aria-current; Hero and Topbar use
  route links too (ButtonLink keeps the button visual)
- PATTERNS + PatternId move to src/data/patterns.ts (no non-component
  export in a component file), pattern buttons gain aria-pressed
- tests/routing.test.tsx: registry/nav invariants, per-route rendering,
  sidebar navigation, pattern deep links, 404

package-lock.json

@@ -10,7 +10,8 @@
       "dependencies": {
         "lucide-react": "^1.45.0",
         "react": "^19.2.8",
-        "react-dom": "^19.2.8"
+        "react-dom": "^19.2.8",
+        "wouter": "^3.11.0"
       },
       "devDependencies": {
         "@testing-library/jest-dom": "^7.0.1",
@@ -2007,6 +2008,15 @@
         "node": ">=8"
       }
     },
+    "node_modules/regexparam": {
+      "version": "3.0.0",
+      "resolved": "https://registry.npmjs.org/regexparam/-/regexparam-3.0.0.tgz",
+      "integrity": "sha512-RSYAtP31mvYLkAHrOlh25pCNQ5hWnT106VukGaaFfuJrZFkGRX5GhUAdPqpSDXxOhA2c4akmRuplv1mRqnBn6Q==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=8"
+      }
+    },
     "node_modules/require-from-string": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/require-from-string/-/require-from-string-2.0.2.tgz",
@@ -2235,6 +2245,15 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/use-sync-external-store": {
+      "version": "1.7.0",
+      "resolved": "https://registry.npmjs.org/use-sync-external-store/-/use-sync-external-store-1.7.0.tgz",
+      "integrity": "sha512-6L+EeigHMQhdaIPNIFUKwfWJSwWFQ8gJbJ2DLOs5sDIegTwR9fRxvnM3uciHKjIZhFz+KAv2emhWMRvDmMcY8A==",
+      "license": "MIT",
+      "peerDependencies": {
+        "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
     "node_modules/vite": {
       "version": "8.3.0",
       "resolved": "https://registry.npmjs.org/vite/-/vite-8.3.0.tgz",
@@ -2461,6 +2480,19 @@
         "node": ">=8"
       }
     },
+    "node_modules/wouter": {
+      "version": "3.11.0",
+      "resolved": "https://registry.npmjs.org/wouter/-/wouter-3.11.0.tgz",
+      "integrity": "sha512-xyMLHhytdGhIjXVRcSjeYbXd7TR1lrxVTPLGBWmmyW52ZuWVQ1jXmsgoJ4G5s4tjloJCq7h4i2eREljWUQ4+/A==",
+      "license": "Unlicense",
+      "dependencies": {
+        "regexparam": "^3.0.0",
+        "use-sync-external-store": "^1.0.0"
+      },
+      "peerDependencies": {
+        "react": ">=16.8.0"
+      }
+    },
     "node_modules/xml-name-validator": {
       "version": "5.0.0",
       "resolved": "https://registry.npmjs.org/xml-name-validator/-/xml-name-validator-5.0.0.tgz",