Support OAuth 2.0 User Context for bookmarks endpoint

[cmtzco]

Problem Description

The x-cli me bookmarks command fails with a 403 error:

RuntimeError: API error (HTTP 403): {
  "title": "Unsupported Authentication",
  "detail": "Authenticating with OAuth 1.0a User Context is forbidden for this endpoint. Supported authentication types are [OAuth 2.0 User Context].",
  "type": "https://api.twitter.com/2/problems/unsupported-authentication",
  "status": 403
}

Expected Behavior

The x-cli me bookmarks command should successfully retrieve the authenticated user's bookmarks using X API v2.

Root Cause

The X API has changed their authentication requirements for the /2/users/{id}/bookmarks endpoint. According to the official X API documentation, this endpoint now requires OAuth 2.0 User Context authentication with the following scopes:

• bookmark.read
• tweet.read
• users.read

Currently, x-cli uses OAuth 1.0a User Context for authenticated read operations (like get_bookmarks, get_mentions). See api.py:L190.

Suggested Fix

Implement OAuth 2.0 User Context authentication in x-cli to support the bookmarks endpoint. This would require:

1. Implementing OAuth 2.0 Authorization Code Flow with PKCE
2. Storing user access tokens and refresh tokens
3. Adding a new authentication method to _oauth2_request() or similar
4. Updating get_bookmarks() to use the OAuth 2.0 authentication method

Impact

This affects:

• x-cli me bookmarks
• x-cli me bookmark
• x-cli me unbookmark
• Potentially other authenticated read endpoints if X updates them similarly

Notes

• Other authenticated read operations (like get_mentions) may also be affected by this X API change
• OAuth 2.0 User Context is different from both OAuth 1.0a and OAuth 2.0 Application-Only (Bearer token)

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