Add an installable `linear-cli` skill

[dubscode]

Summary

Please include an installable linear-cli skill in the CLI's bundled skill catalog.

The CLI already appears to ship a skill system, and there are already bundled skills users can install. It would be useful to have a dedicated skill that teaches agents how to use this CLI correctly.

Proposed command

linear skills install linear-cli

Skill contents

The skill should cover:

• Use linear / li commands with --json for programmatic output.
• Common issue commands:
  • linear issues list --json
  • linear issues get <id> --json
  • linear issues create --input '{...}' --json
  • linear issues update --input '{...}' <id> --json
  • linear issues branch <id-or-identifier> --json
• Accepted issue create/update payload fields.
• Branch-name workflow guidance: prefer linear issues branch over hand-crafted branch names.
• GitHub integration magic words for linking/closing Linear issues.
• Pagination with --limit and --cursor.
• Auth/profile checks via linear auth status --json.
• Guidance for safe batch workflows once batch/filter features exist.

Why this matters

Agents often need durable, tool-specific instructions. A bundled skill would make the recommended CLI usage discoverable and consistent instead of requiring every repo to maintain its own Linear CLI notes.

This is especially helpful because the CLI is agent-friendly already: JSON output, predictable resource/action commands, and canonical branch-name generation.

Expected behavior

• linear skills list shows linear-cli.
• linear skills install linear-cli installs a skill users can load in agent sessions.
• The skill examples stay aligned with the current CLI help and supported flags.