feat(typefully): add X quote post URL support to drafts

[frankdilo]

TL;DR

• Adds quote-post support for X drafts via --quote-post-url (alias --quote-url) on both drafts:create and drafts:update, so CLI users can create/update quote posts without manual payload editing.
• Prevents invalid non-X usage before API calls by returning a clear CLI error when quote flags are used without targeting X, preserving existing non-quote behavior.
• Improves validation feedback from API v2 by surfacing 400 VALIDATION_ERROR responses as explicit validation messages in CLI output.
• Updates docs and test coverage (help text, examples, SKILL.md, changelog, and drafts tests) to keep behavior and guidance aligned.

This adds support for the quote_post_url field in Typefully API v2 create/update draft payloads while keeping backwards compatibility for existing create/update flows.

Testing

• npm test
• npm run test:drafts