Add PR creation action to pane git controls

[Styrse]

Description

Adds a PR action to worktree pane git controls. The action creates a
GitHub pull request with gh pr create --fill, refreshes PR status, and
opens the created PR URL. Also fixes a daemon IPC channel ownership
mismatch for sessions:set-active-session.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING.md guidelines
• My code follows the code style of this project
• I have performed a self-review of my own code
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my
  feature works
• New and existing unit tests pass locally with my changes
• I have run pnpm typecheck and pnpm lint locally
• I have tested the Electron app locally with pnpm electron-dev

Critical Areas Modified

• State management/IPC events