Add followed PR monitoring and creation

[danielss-dev]

Summary

• Persist followed GitHub and Azure DevOps pull requests and automatically follow the checked-out branch’s active PR.
• Poll lightweight activity snapshots on startup, every 60 seconds, and on focus, with coalesced desktop notifications for comments, reviews, failed checks, pushes, and terminal state changes.
• Refresh PR content using stale-while-revalidate behavior so focus, tabs, drafts, and diffs remain in place; stale patches stay readable but cannot receive inline comments.
• Add keyboard-accessible PR and draft creation from the toolbar or command palette through the signed-in provider CLI. Creation never pushes implicitly, then opens and follows the new PR.
• Add the notification integration, typed IPC/provider APIs, and corresponding product documentation.

This keeps reviewers informed without repeatedly reopening or fully reloading PRs, while avoiding unnecessary patch fetches and preserving in-progress review context.

Testing

Added unit coverage for activity-change detection and notification coalescing, follow persistence and mute behavior, failed-poll baseline retention, and provider parsing.

[danielss-dev]

test

[danielss-dev]

test 2

[danielss-dev]

simple test