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>

.trellis/tasks/08-26-direct-manipulation-road-editor/check.jsonl

@@ -0,0 +1,5 @@
+{"file": ".trellis/spec/guides/cross-layer-thinking-guide.md", "reason": "检查跨层数据流是否一致：约束 kind、manifest 字段、API 载荷、客户端类型不得各写一套"}
+{"file": ".trellis/spec/guides/code-reuse-thinking-guide.md", "reason": "检查是否出现第二套米制换算、第二套 ID 校验或重复的 overrides 应用逻辑"}
+{"file": ".trellis/tasks/08-26-direct-manipulation-road-editor/research/joint-solver.md", "reason": "逐条核对约束不变量：最小车道宽、外缘不交叉、路口连续、connector 包含性"}
+{"file": ".trellis/tasks/08-26-direct-manipulation-road-editor/research/junction-tools.md", "reason": "核对编辑所有权与会话边界未被越过：道路 handle 不得进入 junction reserve"}
+{"file": ".trellis/tasks/08-26-direct-manipulation-road-editor/research/current-system.md", "reason": "核对 v1 overrides、feature 回链字段与既有 API 行为未被破坏"}