feat(twitter): add scheduled post commands

[gauravsaxena1997]

Summary

Adds three Twitter/X scheduled post commands:

• twitter schedule to open the X composer scheduler and schedule a text post for a future date/time
• twitter scheduled-list to read visible scheduled posts from the scheduled posts dialog
• twitter scheduled-delete to delete a matching scheduled post with guarded matching and explicit --execute

The implementation keeps scheduled-post writes guarded and browser-based, matching the existing Twitter adapter style.

Details

• Adds shared scheduled-post helpers in clis/twitter/scheduled-utils.js
• Registers the new commands in cli-manifest.json
• Adds adapter tests for command registration, argument validation, browser flow calls, parsing, and guarded delete behavior

Validation

• npm run build
• npm test -- clis/twitter/schedule.test.js clis/twitter/scheduled-list.test.js clis/twitter/scheduled-delete.test.js