feat: planning structure + task 1.2 stack rounding-out

Add .planning/ scaffolding:
- ROADMAP.md (4 phases, 8 non-negotiable design rules)
- phase-1-foundation/ README + 9 task files (1.2-1.10)
- phase-2-live-map / phase-3-dogfood-readiness / phase-4-future README placeholders

Task 1.2 — stack rounding-out:
- Tailwind 4 via @tailwindcss/vite + src/styles/globals.css
- shadcn/ui (slate, new-york) primitives in src/ui/primitives/:
  button, input, label, form, card, alert
- TanStack Router 1.169 + Query 5.100 (devtools + plugin in devDeps)
- Zustand 5, @directus/sdk 21, zod 4, react-hook-form 7 + resolvers
- Prettier 3 + eslint-config-prettier + eslint-plugin-prettier
- ESLint override disabling react-refresh/only-export-components for
  src/ui/primitives/** (intentional dual-exports in shadcn primitives)
- Path alias @/* -> ./src/* in tsconfig.json + tsconfig.app.json
  (TS 6 deprecates baseUrl; paths now resolve relative to config file).
  Pulled forward from 1.3 because shadcn add CLI needs it resolvable.
- Scripts: dev, build, preview, lint, typecheck, format, format:check,
  test (placeholder)
- App.tsx Tailwind smoke test (centred card + shadcn Button)
- README.md rewritten with stack/scripts/shadcn-add docs

All four gates green: typecheck, lint, format:check, build (222KB / 70KB gz).

eslint.config.js

@@ -1,12 +1,13 @@
-import js from '@eslint/js'
-import globals from 'globals'
-import reactHooks from 'eslint-plugin-react-hooks'
-import reactRefresh from 'eslint-plugin-react-refresh'
-import tseslint from 'typescript-eslint'
-import { defineConfig, globalIgnores } from 'eslint/config'
+import js from '@eslint/js';
+import globals from 'globals';
+import reactHooks from 'eslint-plugin-react-hooks';
+import reactRefresh from 'eslint-plugin-react-refresh';
+import tseslint from 'typescript-eslint';
+import prettierRecommended from 'eslint-plugin-prettier/recommended';
+import { defineConfig, globalIgnores } from 'eslint/config';
 
 export default defineConfig([
-  globalIgnores(['dist']),
+  globalIgnores(['dist', 'src/routeTree.gen.ts']),
   {
     files: ['**/*.{ts,tsx}'],
     extends: [
@@ -14,9 +15,18 @@ export default defineConfig([
       tseslint.configs.recommended,
       reactHooks.configs.flat.recommended,
       reactRefresh.configs.vite,
+      prettierRecommended,
     ],
     languageOptions: {
       globals: globals.browser,
     },
   },
-])
+  {
+    // shadcn/ui primitives intentionally co-export helpers (variants, hooks)
+    // alongside components — disable the fast-refresh rule for these files only.
+    files: ['src/ui/primitives/**/*.{ts,tsx}'],
+    rules: {
+      'react-refresh/only-export-components': 'off',
+    },
+  },
+]);