chore(deps): bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/ci.yaml

@@ -10,7 +10,7 @@ jobs:
       name: ✍️ Spelling Check
       runs-on: ubuntu-latest
       steps:
-        - uses: actions/checkout@v4
+        - uses: actions/checkout@v6
         - name: Spell Check
           uses: streetsidesoftware/cspell-action@v6
           with:
@@ -20,20 +20,20 @@ jobs:
     name: 🏗️ Structure Validation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Check For Large Files (under 50KB)
         run: bash ./scripts/check_large_files.sh
   skill-validation:
     name: 📋 Skill Validation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Validate SKILL.md Files
         run: bash ./scripts/validate_skills.sh
   manifest-validation:
     name: 📦 Manifest Validation
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Validate Plugin Manifest
         run: bash ./scripts/validate_plugin_manifest.sh