chore(road-editor): plan direct-edit task tree and add client test infra

Planning: parent design.md becomes the single authoritative contract
(constraint model with 6 kinds, handle manifest, coordinate/unit
layering, preview sequencing, storage layout and lazy migration, area
config snapshot, API contract). Work is split into four independently
verifiable child tasks with per-step gates and rollback points.

Test infra: pin vitest 4.1.11, add test:client:unit for client pure
logic, extend prettier globs to root *.ts so vitest.config.ts is checked.

Add .gitignore: the repo had none, so inputs/, outputs/, workbench-data/
and the client build output were untracked rather than ignored.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

package.json

@@ -14,8 +14,9 @@
     "build": "vite build --config workbench/client/vite.config.ts",
     "dev": "vite --config workbench/client/vite.config.ts",
     "test:client": "tsc --noEmit -p workbench/client/tsconfig.json",
-    "format": "prettier --write \"{src,bin,test,workbench}/**/*.{js,ts,tsx,css,html}\" \"*.{json,js}\"",
-    "format:check": "prettier --check \"{src,bin,test,workbench}/**/*.{js,ts,tsx,css,html}\" \"*.{json,js}\""
+    "test:client:unit": "vitest run --passWithNoTests",
+    "format": "prettier --write \"{src,bin,test,workbench}/**/*.{js,ts,tsx,css,html}\" \"*.{json,js,ts}\"",
+    "format:check": "prettier --check \"{src,bin,test,workbench}/**/*.{js,ts,tsx,css,html}\" \"*.{json,js,ts}\""
   },
   "dependencies": {
     "fflate": "0.8.3",
@@ -29,6 +30,7 @@
     "@types/react-dom": "^19.0.3",
     "prettier": "^3.9.6",
     "typescript": "^5.7.3",
-    "vite": "^6.1.0"
+    "vite": "^6.1.0",
+    "vitest": "4.1.11"
   }
 }