Add Command to pull user-facing skills

[yihao03]

What is the purpose of this pull request?

• Documentation update
• Bug fix
• Feature addition or enhancement
• Code maintenance
• DevOps
• Improve developer experience
• Others, please explain:

Overview of changes:
As a part of #2869: create skills for MarkBind users, This PR adds a new command: markbind skills that pulls skills for the MarkBind Skills repository and add them to user's MarkBind project root.

We foresee changes made to MarkBind such that the skills will no longer be consistent with actual MarkBind features and/or configurations. Therefore, we have implemented a version control system by writing a .markbind-skills.json file to .agents/skills to keep track of the version of skills that the user has. This allows us to prompt users to update their skills if they are inconsistent with the package.json aiSkillsVersion field.

Anything you'd like to highlight/discuss:
This PR also includes a new package @inquirer/prompts to handle interactive prompt for users to idenfity the coding harnesses used and create symlinks accordingly. This is a step towards #2888

Testing instructions:
Pull this branch and run markbind skills to test out all the commands.

Proposed commit message: (wrap lines at 72 characters)
Add markbind skills command to pull MarkBind Skills from GitHub

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Checklist: ☑️

• Updated the documentation for feature additions and enhancements
• Added tests for bug fixes or features
• Linked all related issues
• No unrelated changes

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Reviewer checklist:

Indicate the SEMVER impact of the PR:

• Major (when you make incompatible API changes)
• Minor (when you add functionality in a backward compatible manner)
• Patch (when you make backward compatible bug fixes)

At the end of the review, please label the PR with the appropriate label: r.Major, r.Minor, r.Patch.

Breaking change release note preparation (if applicable):

• To be included in the release note for any feature that is made obsolete/breaking

Give a brief explanation note about:

• what was the old feature that was made obsolete
• any replacement feature (if any), and
• how the author should modify his website to migrate from the old feature to the replacement feature (if possible).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.35%. Comparing base (3132728) to head (9da4f48).

Additional details and impacted files

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##           master    #2891    +/-   ##
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  Coverage   71.35%   71.35%            
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  Files         133      133            
  Lines        7229     7229            
  Branches     1580     1704   +124     
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  Hits         5158     5158            
+ Misses       2065     1970    -95     
- Partials        6      101    +95     

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[Copilot]

Pull request overview

Adds a new CLI workflow for downloading and installing “MarkBind Skills” into a MarkBind project, including version tracking via a metadata file and optional agent-specific symlink setup.

Changes:

• Introduces packages/cli/src/cmd/skills.ts implementing git-based download, install, and .markbind-skills.json metadata management.
• Adds markbind skills command group with install and update subcommands and an interactive agent selection prompt.
• Adds unit tests for the skills installer logic and related helpers.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
packages/cli/src/cmd/skills.ts	Implements skills download/install, metadata read/write, semver comparison, and agent symlinking.
packages/cli/index.ts	Wires new skills commands into the CLI and adds interactive prompting for agent selection.
packages/cli/package.json	Adds aiSkillsVersion and the @inquirer/prompts dependency.
packages/cli/test/unit/skills.test.ts	Adds unit tests covering installer behavior, metadata, semver logic, and symlinks.
package-lock.json	Updates lockfile to include @inquirer/* dependency tree and related metadata changes.

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[MoshiMoshiMochi]

Perhaps we can consider adding a check to ensure that the command is run inside a markbind directory

[MoshiMoshiMochi]

LGTM

[github-actions]

@MoshiMoshiMochi Each PR must have a SEMVER impact label, please remember to label the PR properly.