ci: bump checkout v4→v7 and setup-python v5→v6

Clears the Node.js 20 deprecation annotation on Actions runs: checkout is on
Node 24 from v5 and setup-python from v6, so v7 / v6 both run on Node 24. Pins
the moving major tags (@v7, @v6) to match the repo's existing convention and
keep picking up patch fixes. No workflow logic change; the local reusable-
workflow reference (./.github/workflows/checks.yml) is untouched.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ff8r7ajo54cRPm8v5MU4qr

Author: Imbad0202

.github/workflows/checks.yml

@@ -23,8 +23,8 @@ jobs:
         # current baseline.
         python-version: ["3.9", "3.12"]
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+      - uses: actions/checkout@v7
+      - uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python-version }}
       - name: Manifest parse lint

.github/workflows/release.yml

@@ -21,8 +21,8 @@ jobs:
     needs: checks
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
+      - uses: actions/checkout@v7
+      - uses: actions/setup-python@v6
         with:
           python-version: "3.12"
       - name: Release-only gates