Update GitHub Pages documentation site

[Pratiyush]

Description

Update the GitHub Pages deployment and documentation site to reflect:

• New repo name (skill-sdk)
• Updated navigation links
• Updated API reference docs
• Ensure all internal cross-links work correctly after rename
• Rebuild and redeploy docs site

Acceptance Criteria

• All docs pages render correctly at new URL
• No broken internal links
• Specification, concepts, tutorial pages all updated
• GitHub Pages workflow deploys successfully