feat: Local lock when saving skills to project scope, and sync from node_modules

[quuu]

This pull request introduces project-local skill lock file support and a new experimental sync command to the skills CLI. The main changes add a new skills-lock.json file for project-scoped skill tracking, update the add command to write to this file, and introduce the experimental_sync command to sync skills from node_modules. Documentation and CLI help output are updated to reflect these features.

Project-local skill lock file and sync support:

• Added a new module src/local-lock.ts that implements reading, writing, and hashing for a project-local skills-lock.json file, enabling deterministic and merge-friendly tracking of project-specific skills.
• Updated the add command in src/add.ts to write installed skills to the local lock file (skills-lock.json) for project-scoped installs, including a computed hash of the skill directory. [1] [2] [3] [4]

Experimental sync command:

• Introduced the experimental_sync command, implemented in src/sync.ts (referenced in docs and CLI), to crawl node_modules and sync discovered skills into agent directories and the local lock file. [1] [2] [3] [4] [5] [6]

CLI and documentation updates:

• Improved CLI banner, help, and examples to document the new experimental_sync command and clarify project vs. global skill management. [1] [2] [3] [4]
• Expanded AGENTS.md with details about the new lock files and sync command. [1] [2]

Telemetry:

• Added telemetry event type for experimental_sync to src/telemetry.ts.