fix: add .github/labels.yml for Automatic Label Sync workflow

[RedStar071]

The reusable label-sync workflow merges this file with the shared sapphiredev/.github core labels, but it was missing here, causing the workflow to fail (open overwrite-labels/.github/labels.yml: no such file or directory).

🔗 Linked issue

🧭 Context

📚 Description

Key changes

Type of Change

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation change
• Workflow / CI change

Pre-flight Checklist

• I have read the Contributing Guidelines (if applicable)
• My code follows the code style of this project
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have updated the documentation accordingly
• I added a changeset with pnpm changeset (or pnpm changeset add --empty if no release is needed). See .changeset/README.md.

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Confidence Score: 4/5

The PR appears safe to merge, with a non-blocking cleanup needed for the unused plugins-subcommands-advanced package label.

The manifest is valid and supplies the workflow's missing input, while one newly synchronized label has no corresponding workspace package or path-labeler rule.

Files Needing Attention: .github/labels.yml

T-Rex Logs

What T-Rex did

• Validated the general contract by observing that the process now exits with code 0 instead of 1 when .github/labels.yml was absent from HEAD^.
• Confirmed the run reports yaml_parse=ok and lists 8 label names.
• Confirmed a pinned reusable workflow is detected and merge_labels_enabled is true.

_{Ran code and verified through T-Rex}

Prompt To Fix All With AI

### Issue 1
.github/labels.yml:21-23
**Unused package label definition**

`packages:plugins-subcommands-advanced` has no corresponding workspace package or path-labeler mapping, so label sync maintains a dead label that clutters the repository label namespace.

```suggestion

```

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "fix: add .github/labels.yml for Automati..." | Re-trigger Greptile}

Greptile also left 1 inline comment on this PR.

[lorypelli]

LGTM!

[greptile-apps]

Unused package label definition

packages:plugins-subcommands-advanced has no corresponding workspace package or path-labeler mapping, so label sync maintains a dead label that clutters the repository label namespace.

Suggested change

	- name: packages:plugins-subcommands-advanced
	color: "1d76db"
	description: Changes in plugins-subcommands-advanced

Prompt To Fix With AI

This is a comment left during a code review.
Path: .github/labels.yml
Line: 21-23

Comment:
**Unused package label definition**

`packages:plugins-subcommands-advanced` has no corresponding workspace package or path-labeler mapping, so label sync maintains a dead label that clutters the repository label namespace.

```suggestion

```

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.