SP-348: Add command to retrieve single skill files

[Thomas Neumüller (tneum-celonis)]

Description

Adds a new asset-registry skills get command for downloading skill files registered in the asset registry. By default it fetches SKILL.md for the given --path; pass --file <relative> to retrieve any reference file bundled with the skill, and --output <dir> to choose a destination directory (defaults to cwd).

Also refactors a few small bits along the way:

• Extracts a shared trimSlashes helper in src/core/utils/path.ts (used by both the service and the URL-building code).
• FileService.writeBufferToPath now reuses writeBufferToFileWithGivenName for the actual write, and a new private ensureDir helper replaces every fs.mkdirSync(..., { recursive: true, mode: ... }) call in the file.

Relevant links

• Jira: SP-348

Checklist

• I have self-reviewed this PR
• I have tested the change and proved that it works in different scenarios
• I have updated docs if needed

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
1 Accepted issue

Measures
0 Security Hotspots
94.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud