ci: backport PR validation scripts to skill branch

[rajshah4]

Summary

• Backports the PR description and issue readiness validation scripts and workflows from main onto skill/openhands-enterprise-troubleshooting.
• Restores .github/scripts/, the two validation workflows, and .github/dependabot.yml so pull_request_target checks out a base SHA that contains the script they run.
• No changes to skill content; this is .github infrastructure only.

Why

PR #457 fails the Validate PR description check with:

python: can't open file '/home/runner/work/extensions/extensions/.github/scripts/check_pr_description.py': [Errno 2] No such file or directory

pr-description-check.yml uses pull_request_target and checks out github.event.pull_request.base.sha. For #457 the base branch is skill/openhands-enterprise-troubleshooting, which predates these scripts. The workflow file exists (inherited at branch creation) but the script it invokes does not, so the job errors out on file-not-found rather than on PR description problems.

Retargeting #457 to main would change the intended merge strategy (#457 is explicitly built on top of #456). Backporting the scripts onto the skill branch is the minimal fix.

Validation

All seven restored entries match main content.

Source Verification

Claim	Source
Workflow runs on pull_request_target and checks out github.event.pull_request.base.sha	pr-description-check.yml
main contains .github/scripts/check_pr_description.py; the skill branch does not	main vs skill/openhands-enterprise-troubleshooting
PR #457 base is skill/openhands-enterprise-troubleshooting	PR #457

This pull request was created by an AI agent (OpenHands) on behalf of Rajiv Shah.

[all-hands-bot]

👋 This PR needs a couple of things fixed before OpenHands can review it:

• the PR description's HUMAN: section needs at least 20 characters describing what you tested, not just the template placeholder

Push an update once this is addressed and this check re-runs automatically.

This is an automated check - no AI was used to generate this comment.

[all-hands-bot]

👋 This PR needs a couple of things fixed before OpenHands can review it:

• the PR description's HUMAN: section needs at least 20 characters describing what you tested, not just the template placeholder

Push an update once this is addressed and this check re-runs automatically.

This is an automated check - no AI was used to generate this comment.