✨ feat(skills): add todo-plan skill

SKILLS.md

@@ -162,6 +162,7 @@ sh docs/standards/playbook/scripts/install_codex_skills.sh
 
 - `commit-message`：基于 staged diff 自动建议提交信息（`:emoji: type(scope): subject`）
 - `create-plan`：生成简明计划（适用于用户明确要求规划编码任务）
+- `todo-plan`：按模板追加计划到 TODO.md（触发词：plan/计划/TODO/待办；自动合并/拆分）
 - `code-review-workflow`：结构化代码评审（正确性/安全/性能/测试）
 - `style-cleanup`：整理代码风格（优先使用仓库既有 formatter/lint 工具链）
 - `bulk-refactor-workflow`：批量重构（安全做法 + 验证契约）

codex/skills/todo-plan/SKILL.md

@@ -0,0 +1,47 @@
+---
+name: todo-plan
+description: "Create and append plan blocks to TODO.md when the user asks for a plan or mentions plan/计划/TODO/待办; auto-merge or split related tasks."
+---
+
+# TODO Plan Writer
+
+## Trigger guard
+
+- Only run if the user message explicitly contains one of: `plan`, `计划`, `TODO`, `待办`.
+
+## Output target
+
+- Append plan blocks to `TODO.md` (at file end).
+- Do not modify other files.
+
+## Planning rules
+
+- Use create-plan style reasoning: intent -> scope -> action items; include validation/risks when relevant.
+- Title: concise "module + action" (2-6 words or 6-12 chars).
+- Multiple tasks:
+  - Merge into one Plan if same module/goal.
+  - Split if different modules/goals.
+
+## Formatting rules
+
+- Use the template below verbatim.
+- Keep existing TODO.md English structure and indentation.
+- Use `[ ]` for each action item line.
+- If notes are not obvious, use `- TBD`.
+- Line endings: LF.
+
+## Plan template
+
+```md
+## Plan: <title>
+
+- Goal: <one-line objective>
+- Scope:
+  - In: <what is included>
+  - Out: <what is excluded>
+- Actions:
+  [ ] <action item>
+  [ ] <action item>
+- Notes:
+  - <tests / observations / constraints>
+```