chore(skills): add git checkpoint commit loop

.codex/skills/git-checkpoint-commit/SKILL.md

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+---
+name: git-checkpoint-commit
+description: Use when a coding task finishes a verified bug fix, key feature, risky refactor checkpoint, local backup commit, checkpoint commit, 提交备份, 本地提交, or when an active session has accumulated about five meaningful edit rounds and should create a scoped local git commit without pushing.
+---
+
+# Git Checkpoint Commit
+
+## Overview
+
+Use this skill to keep a local git backup loop during active development. The goal is to commit verified, task-scoped progress at meaningful checkpoints without mixing unrelated user changes or pushing remotely.
+
+## Trigger Rules
+
+Create a local checkpoint commit when any condition is true:
+
+- A bug fix is implemented and the targeted regression check passes.
+- A key feature slice is implemented and the smallest relevant verification passes.
+- A risky refactor reaches a behavior-preserving checkpoint.
+- The current session has reached about five meaningful edit rounds since the last commit.
+- The user asks for `提交`, `本地提交`, `备份`, `checkpoint`, `commit`, or `形成提交循环`.
+
+Do not use this skill when the user explicitly says not to commit, when the change is exploratory and unverified, or when the only available commit would include unrelated dirty files.
+
+## Workflow
+
+1. Inspect the working tree with `git status --short`.
+2. Identify files or hunks owned by the current task.
+3. Run the smallest relevant verification first.
+   - In X-Financial, run backend tests inside `x-financial-main` when backend code is involved.
+   - Use targeted frontend tests/builds for web-only changes.
+4. Commit only the task-owned files.
+5. Report the commit hash and verification evidence.
+6. Reset the session edit counter to zero after a successful checkpoint.
+
+## Safety Rules
+
+- Never commit unrelated user changes just to make the tree clean.
+- Never push as part of this skill.
+- Never rewrite history, amend old commits, or run destructive git commands.
+- If the same file contains unrelated hunks, split the staging carefully with `git add -p` or a narrower manual patch.
+- If the index already contains staged changes, inspect them first; do not mix them into a checkpoint unless they belong to the same current task.
+- If verification cannot run, say why in the commit body or final report and prefer a `chore(checkpoint)` message rather than a confident `fix` or `feat`.
+
+## Commit Style
+
+Use normal semantic messages for completed, verified work:
+
+- `fix(workbench): keep application preview after draft save failure`
+- `feat(reimbursements): add attachment association job polling`
+- `refactor(claims): split draft flow serialization`
+
+Use checkpoint messages for interim backup points:
+
+- `chore(checkpoint): backup attachment association flow`
+- `chore(checkpoint): backup after five edit rounds`
+
+Keep the subject concise. Add body lines only when the verification state or scope needs clarity.
+
+## Helper Script
+
+Use `scripts/checkpoint_commit.py` when a path-scoped local commit is enough:
+
+```bash
+python3 .codex/skills/git-checkpoint-commit/scripts/checkpoint_commit.py \
+  --message "chore(checkpoint): backup workbench AI flow" \
+  web/src/composables/workbenchAiMode/useWorkbenchAiExpenseFlow.js \
+  web/tests/workbench-ai-mode-switch.test.mjs
+```
+
+Preview before committing:
+
+```bash
+python3 .codex/skills/git-checkpoint-commit/scripts/checkpoint_commit.py \
+  --dry-run \
+  web/src/utils/expenseApplicationPreview.js
+```
+
+The script refuses to commit the whole tree unless `--allow-all` is passed. Use `--allow-all` only when the current task truly owns every dirty file.
+
+## Common Mistakes
+
+- Mistaking backup for verification. Verify first, then commit.
+- Staging `.` in a dirty worktree. Stage explicit paths or hunks.
+- Combining documentation cleanup, feature work, and unrelated local edits in one checkpoint.
+- Continuing indefinitely after multiple verified slices. Commit once the counter reaches five meaningful edit rounds.