chore(deps): bump actions/checkout from 4 to 6 (#10)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -24,7 +24,7 @@ jobs:
         os: [windows-latest, macos-latest, ubuntu-latest]
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-python@v5
         with:
@@ -44,7 +44,7 @@ jobs:
     needs: smoke
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-python@v5
         with:

.github/workflows/labels.yml

@@ -16,7 +16,7 @@ jobs:
   sync:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: EndBug/label-sync@v2
         with:
           config-file: .github/labels.yml

.github/workflows/lint.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - uses: actions/setup-python@v5
         with:
           python-version: "3.12"

.github/workflows/release.yml

@@ -52,7 +52,7 @@ jobs:
     timeout-minutes: 30
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-python@v5
         with:
@@ -81,7 +81,7 @@ jobs:
     timeout-minutes: 60
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       # System Python (used by build script to find tkinter for bundling)
       - uses: actions/setup-python@v5
@@ -120,7 +120,7 @@ jobs:
       PKG_SIGN_IDENTITY: "Developer ID Installer: Siddharth Sachar (33PQRTZLNW)"
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       # ── Import Apple certificates into a temporary keychain ────────────────
       - name: Import Apple certificates

.github/workflows/update-manifest.yml

@@ -31,7 +31,7 @@ jobs:
     timeout-minutes: 10
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: actions/setup-python@v5
         with: