docs: refresh AgentID guides for current SDK and CLI

[sidharth0612]

Summary

The AgentID guides mixed current API routes with removed key-management methods and transaction-signing examples. Update the sign-in and public-key guides, CLI reference, and related changelogs to use the current API Keys lifecycle, auth_token, and accept_disclosure.

• Replace browser-focused enrollment content with provider connect, pending sign-in authorization, activation checks, and credential management.
• Move the sign-in guide to /agentid-sign-in and permanently redirect its previous URL.
• Verify examples against TypeScript SDK 0.5.25 and CLI 1.4.0. Use Python HTTP examples because published Python SDK 0.5.10 lacks the current endpoints.
• Remove JTI-based approval examples, obsolete methods, and outdated permission claims.

Validation

• Five TypeScript examples compile against the published SDK with strict checking.
• Eight CLI examples pass dry runs using CLI 1.4.0; no API requests sent.
• Six changed MDX pages compile; five Python examples pass syntax parsing.
• npm run lint and git diff --check pass.
• fern check --local: zero errors; 30 warnings in unchanged API schemas and unrelated changelog entries.
• Terminology, navigation, and permanent redirect checks pass.

[github-actions]

🌿 Preview your docs: https://agentmail-preview-edfacd28-6445-4241-85b5-e22ce9e564a5.docs.buildwithfern.com

[github-actions]

🌿 Preview your docs: https://agentmail-preview-00edcc0a-5d3b-4fd8-b570-710338084888.docs.buildwithfern.com