Add Xquik skill and repair Playwright guide links

[kriptoburak]

Summary

• Add a canonical Xquik Skill for REST, MCP, webhooks, extractions, monitors, and approved X actions.
• Repair broken navigation across the Playwright page-object, migration, test-organization, and CI guides.

Independent repair

Several Playwright references targeted nonexistent core, foundations, decisions, or infrastructure paths. The corrected links now follow the repository’s actual pom, core, and ci layout.

Validation

• Rebuilt the branch on current main.
• Passed the canonical Skill validator.
• Resolved all 567 local Playwright Markdown links.
• Rendered all 5 changed Markdown files through GitHub.
• Verified the documented Xquik entry points.
• Passed git diff --check.

[kriptoburak]

I rebuilt this PR on current main and signed the replacement commit. It now includes a concrete independent repair: broken Playwright guide links across page-object, migration, test-organization, and CI references all point to their actual files. The Xquik Skill also follows the current canonical schema and documents present REST, MCP, security, approval, and write-recovery contracts. All 567 local Playwright links resolve, all changed Markdown renders through GitHub, and git diff --check passes.