ci: add workflow to warn PRs modifying frozen bash scripts

The bash implementations of kubectx/kubens are frozen and no longer
accepting improvements. This workflow comments on PRs that modify these
files to redirect contributors to the Go implementation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/bash-frozen.yml

@@ -0,0 +1,35 @@
+name: Bash scripts frozen
+
+on:
+  pull_request:
+    paths:
+      - 'kubectx'
+      - 'kubens'
+
+jobs:
+  comment:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - name: Comment on PR if author is not ahmetb
+        if: github.event.pull_request.user.login != 'ahmetb'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const body = [
+              '> [!WARNING]',
+              '> **This PR will not be merged.**',
+              '>',
+              '> The bash implementation of `kubectx` and `kubens` is **frozen** and is provided only for convenience.',
+              '> We are not accepting any improvements to the bash scripts.',
+              '>',
+              '> Please propose your improvements to the **Go implementation** instead.',
+            ].join('\n');
+
+            await github.rest.issues.createComment({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+              body: body
+            });