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>

vitest.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from 'vitest/config';
+
+// 只覆盖客户端纯逻辑（EditSession 命令栈、previewSeq 仲裁、handle 事件到约束值的投影、米制换算）。
+// OpenLayers 地图行为不在此处测试，见各子任务 implement.md 的手测清单。
+export default defineConfig({
+  test: {
+    include: ['workbench/client/src/**/*.test.ts'],
+    environment: 'node',
+  },
+});