ci: add pull_request trigger for release-drafter autolabeler

[Aaron ("AJ") Steers (aaronsteers)]

Summary

Fixes release-drafter not grouping PRs into categories by adding the pull_request trigger. The autolabeler feature requires this trigger to apply labels when PRs are opened/updated - without it, PRs never get labels, so release notes show all items ungrouped.

Also updates the concurrency group to be event-specific, preventing PR runs from blocking push-to-main runs.

Review & Testing Checklist for Human

• Verify that the release-drafter action only runs the autolabeler (not release draft updates) on pull_request events - check release-drafter docs
• Test by opening a PR with a conventional commit title (e.g., feat: test) and confirm the appropriate label is applied automatically
• After merging, verify the next release draft groups items correctly under category headers

Notes

Requested by: Aaron ("AJ") Steers (@aaronsteers)
Devin session: https://app.devin.ai/sessions/7e4f7a26a67248bf8d475999269a07c3

[devin-ai-integration]

Original prompt from AJ Steers

Received message in Slack channel #ask-devin-ai:

@Devin - Release drafter isn't properly grouping items in the new airbytehq/fastmcp-extensions repo. Please investigate.
Thread URL: https://airbytehq-team.slack.com/archives/C08BHPUMEPJ/p1768689931936339

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR. Add '(aside)' to your comment to have me ignore it.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring

[github-actions]

🎉 Thanks for opening this pull request!

Your contribution is appreciated. Here are some helpful commands you can use:

Quick Commands

• /autofix - Auto-format and fix linting issues (ruff format + ruff check --fix)
• /lock - Update the uv.lock file with latest dependencies

Available Poe Tasks

You can run any of these tasks using the slash command: /poe <task-name>

Core Tasks

• /poe test - Run all tests
• /poe test-fast - Run tests with fast exit on first failure
• /poe lint - Check code style and quality
• /poe format - Format code with ruff
• /poe deps - Check for unused and missing dependencies
• /poe check - Run format check, linting, dependency check, and tests

Quick Fixes

• /poe fix - Auto-format and fix linting issues
• /poe clean - Clean up build artifacts and cache

Build & Install

• /poe build - Build the package
• /poe install - Install with development dependencies

Other Commands

• /poe version - Show package version
• /poe pre-commit - Run pre-commit style checks

The CI will automatically run tests when you push commits. Happy coding! 🚀

[devin-ai-integration]

Closing this PR - the actual issue was missing labels in the repository, not the workflow configuration. The missing labels (chore, docs, testing, security, dependencies, breaking) have been created directly in the repo.