feat(ci): refine PR business area labels and introduce skill format check

.github/workflows/pr-labels-test.yml

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+name: Test PR Label Logic
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "scripts/pr-labels/**"
+      - ".github/workflows/pr-labels-test.yml"
+  pull_request:
+    branches: [main]
+    paths:
+      - "scripts/pr-labels/**"
+      - ".github/workflows/pr-labels-test.yml"
+
+permissions:
+  contents: read
+
+jobs:
+  test-pr-labels:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Run PR label regression tests
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: node scripts/pr-labels/test.js

.github/workflows/pr-labels.yml

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+name: PR Labels
+
+on:
+  pull_request_target:
+    # NOTE: This event runs with base-branch code and write permissions.
+    # Do NOT add `ref: github.event.pull_request.head.sha` to the checkout step,
+    # as that would execute untrusted PR code with elevated access.
+    types:
+      - opened
+      - edited
+      - reopened
+      - synchronize
+      - ready_for_review
+
+permissions:
+  contents: read
+  pull-requests: write
+  issues: write
+
+jobs:
+  sync-pr-labels:
+    if: ${{ github.event.pull_request.state == 'open' }}
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Sync managed PR labels
+        id: sync_pr_labels
+        # Labeling is best-effort and must not block PR merges.
+        continue-on-error: true
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: node scripts/pr-labels/index.js
+
+      - name: Warn when label sync fails
+        if: ${{ always() && steps.sync_pr_labels.outcome == 'failure' }}
+        run: |
+          echo "::warning::PR label sync failed; labels may be stale."
+          echo "⚠️ PR label sync failed; labels may be stale." >> "$GITHUB_STEP_SUMMARY"

.github/workflows/skill-format-check.yml

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+name: Skill Format Check
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "skills/**"
+      - "scripts/skill-format-check/**"
+      - ".github/workflows/skill-format-check.yml"
+  pull_request:
+    branches: [main]
+    paths:
+      - "skills/**"
+      - "scripts/skill-format-check/**"
+      - ".github/workflows/skill-format-check.yml"
+
+permissions:
+  contents: read
+
+jobs:
+  check-format:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: Run Skill Format Check
+        run: node scripts/skill-format-check/index.js

scripts/pr-labels/README.md

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+# PR Label Sync
+
+This directory contains scripts and sample data for automatically classifying and labeling GitHub Pull Requests based on the files they modify.
+
+## Files
+
+- `index.js`: The main Node.js script. It fetches PR files, evaluates their risk level, calculates business impact, and uses GitHub APIs to add appropriate `size/*` and `domain/*` labels.
+- `samples.json`: A collection of historical PRs used as test cases to verify the labeling logic (especially for regression testing the S/M/L thresholds).
+
+## Features
+
+### Size Labels (`size/*`)
+The script evaluates the "effective" lines of code changed (ignoring tests, docs, and ci files) to classify the PR:
+- **`size/S`**: Low-risk changes involving only docs, tests, CI workflows, or chores.
+- **`size/M`**: Small-to-medium changes affecting a single business domain, with effective lines under 300.
+- **`size/L`**: Large features (>= 300 lines), cross-domain changes, or any changes touching core architecture paths (like `cmd/`).
+- **`size/XL`**: Architectural overhauls, extremely large PRs (>1200 lines), or sensitive refactors.
+
+### Domain Tags (`domain/*`)
+The script also identifies which business domains a PR touches to give reviewers an immediate sense of the impact scope. Currently tracked domains include:
+- `domain/im`
+- `domain/vc`
+- `domain/ccm`
+- `domain/base`
+- `domain/mail`
+- `domain/calendar`
+- `domain/task`
+- `domain/contact`
+
+Minor modules like docs and tests are omitted to keep PR tags clean and focused on structural changes.
+
+## Usage
+
+### In GitHub Actions
+This script is designed to run in CI workflows. It automatically reads the `GITHUB_EVENT_PATH` payload to get the PR context.
+
+```bash
+node scripts/pr-labels/index.js
+```
+
+### Local Dry Run
+You can test the labeling logic against an existing GitHub PR without actually applying labels by using the `--dry-run` flag.
+
+```bash
+# Requires GITHUB_TOKEN environment variable or passing --token
+node scripts/pr-labels/index.js --dry-run --repo larksuite/cli --pr-number 123
+```
+
+## Testing
+
+A regression test suite is available in `test.js` which verifies the output of the classification logic against historical PRs configured in `samples.json`.
+
+```bash
+# Requires GITHUB_TOKEN environment variable to avoid rate limits
+GITHUB_TOKEN=$(gh auth token) node scripts/pr-labels/test.js
+```
+
+This test suite also runs automatically in CI via `.github/workflows/pr-labels-test.yml` when changes are made to this directory.