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>

.gitignore

@@ -0,0 +1,13 @@
+node_modules/
+
+# 本机独有的编译输入（体积大、按区域各异，不入库）
+inputs/
+
+# 编译与测试产物
+outputs/
+workbench/client/dist/
+
+# 工作台运行期数据：导入的 OSM、overrides、信号与派生产物
+workbench-data/
+
+.DS_Store