Request dm.read and dm.write on the X plugin

[vaulpannx]

Summary

• Add dm.read and dm.write to the X plugin OAuth scope list in third_party/x/mcp.json, matching the Chat endpoints xmcp is exposing.
• Mirror the scopes in README, bump the plugin to 2.4.0, and note in the changelog that existing installs must sign in to X again.

Test plan

• python3 -m json.tool on mcp.json, plugin.json, and marketplace.json
• After merge, a fresh X plugin Connect prompt includes dm.read and dm.write
• Existing installs re-auth to X and the token carries the new scopes

Made with Cursor

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