fix: harden GitHub Actions workflows (#2021)

Author: dagecko

.github/workflows/lint.yml

@@ -15,7 +15,7 @@ jobs:
         uses: actions/checkout@v6
 
       - name: Run markdownlint-cli2
-        uses: DavidAnson/markdownlint-cli2-action@v23
+        uses: DavidAnson/markdownlint-cli2-action@ce4853d43830c74c1753b39f3cf40f71c2031eb9 # v23
         with:
           globs: |
             '**/*.md'

.github/workflows/test.yml

@@ -16,7 +16,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v7
+        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7
 
       - name: Set up Python
         uses: actions/setup-python@v6
@@ -36,7 +36,7 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Install uv
-        uses: astral-sh/setup-uv@v7
+        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7
 
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v6