Upgrade GitHub Actions for Node 24 compatibility (#119)

## Summary

Upgrade GitHub Actions to their latest versions to ensure compatibility
with Node 24, as Node 20 will reach end-of-life in April 2026.

## Changes

| Action | Old Version(s) | New Version | Release | Files |
|--------|---------------|-------------|---------|-------|
| `actions/checkout` |
[`v4`](https://github.com/actions/checkout/releases/tag/v4) |
[`v6`](https://github.com/actions/checkout/releases/tag/v6) |
[Release](https://github.com/actions/checkout/releases/tag/v6) |
main.yml, pull_request.yml, pull_request_label.yml |

## Context

Per [GitHub's
announcement](https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/),
Node 20 is being deprecated and runners will begin using Node 24 by
default starting March 4th, 2026.

### Why this matters

- **Node 20 EOL**: April 2026
- **Node 24 default**: March 4th, 2026
- **Action**: Update to latest action versions that support Node 24

### Security Note

Actions that were previously pinned to commit SHAs remain pinned to SHAs
(updated to the latest release SHA) to maintain the security benefits of
immutable references.

### Testing

These changes only affect CI/CD workflow configurations and should not
impact application functionality. The workflows should be tested by
running them on a branch before merging.

Signed-off-by: Salman Muin Kayser Chishti <13schishti@gmail.com>

Author: salmanmkc

.github/workflows/main.yml

@@ -72,7 +72,7 @@ jobs:
       integration-test-matrix: '${{ steps.generate-matrix.outputs.integration-test-matrix }}'
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           persist-credentials: false
       - id: generate-matrix
@@ -101,7 +101,7 @@ jobs:
       example-packages-matrix: '${{ steps.generate-matrix.outputs.example-packages-matrix }}'
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           persist-credentials: false
       - id: generate-matrix

.github/workflows/pull_request.yml

@@ -79,7 +79,7 @@ jobs:
       integration-test-matrix: '${{ steps.generate-matrix.outputs.integration-test-matrix }}'
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           persist-credentials: false
       - id: generate-matrix
@@ -108,7 +108,7 @@ jobs:
       example-packages-matrix: '${{ steps.generate-matrix.outputs.example-packages-matrix }}'
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           persist-credentials: false
       - id: generate-matrix

.github/workflows/pull_request_label.yml

@@ -14,7 +14,7 @@ jobs:
     timeout-minutes: 1
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           persist-credentials: false
       - name: Check for Semantic Version label