fix: update GitHub Actions to actual latest versions

Update action versions from outdated pins to current releases:

- actions/checkout: v4.2.2 → v5.0.1 (SHA 93cb6efe, published 2025-11-17)
- lycheeverse/lychee-action: v2.1.0 → v2.7.0 (SHA a8c4c7cb, published 2025-10-29)

Previous commit used outdated versions. This updates to the actual latest
releases for improved security and features.

🤖 Generated with Claude Code

Co-Authored-By: Claude <[email protected]>

Author: btiernay

.github/workflows/link-check.yml

@@ -45,7 +45,7 @@ jobs:
     steps:
     # Fetch repository contents so Lychee can scan Markdown / MDX files
     - name: Checkout repo
-      uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683  # v4.2.2
+      uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd  # v5.0.1
 
     # Run Lychee on the current docs tree from the matrix.
     #
@@ -69,7 +69,7 @@ jobs:
     # filtered via .lycheeignore in the repo root.
     - name: Run Lychee on ${{ matrix.site.name }} docs
       id: lychee
-      uses: lycheeverse/lychee-action@2ab282516ba6ed0a7c49a30ce0c92acdcf43e1c8  # v2.1.0
+      uses: lycheeverse/lychee-action@a8c4c7cb88f0c7386610c35eb25108e448569cb0  # v2.7.0
       env:
         # Used by Lychee for authenticated GitHub requests to reduce rate limiting.
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}