Add Intercom article draft bridge

[EdgeClaws]

Summary

• add a dedicated authenticated DigitalOcean function for Intercom article drafts
• create new articles as drafts and upload drafts for existing articles
• stage edits for published articles without changing the live version
• return a direct authenticated Knowledge editor URL for manual review and publish
• document request/response shapes and required environment variables

Test plan

• 62 pytest tests pass (new draft-bridge tests plus the existing Intercom suite)
• Python compile check passes
• project.yml parses successfully
• git diff --check passes

Deployment

Not deployed by this PR. The DigitalOcean package needs INTERCOM_ARTICLE_ACCESS_TOKEN, INTERCOM_DRAFT_BRIDGE_SECRET, and INTERCOM_ARTICLE_AUTHOR_ID configured before deployment.