feat(app): add delete session with confirmation dialog

[ohsalmeron]

Issue for this PR

Closes #36962

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds a right-click/context menu option "Delete Session" to session items in the sidebar. Clicking it opens a confirmation dialog, and confirming it calls the DELETE API on the session, cleanly removing it from both local state and backend.

How did you verify your code works?

Tested right-clicking a session, triggering the delete option, confirming the modal, and checking that the session was correctly deleted and removed from the list.

Screenshots / recordings

Delete option in the sidebar session menu and the confirmation modal.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Duplicate PRs Found

#33208

• Title: feat(app): add delete button for sessions in sidebar
• Why it's related: This PR also adds a delete feature for sessions in the sidebar, which is very similar to the current PR's functionality of adding a delete session option via context menu.

#11684

• Title: feat(tui): add session delete command with confirmation dialog
• Why it's related: This PR implements session deletion with a confirmation dialog, but for the TUI instead of the app. It may share design patterns or logic that could be relevant for consistency.

[ohsalmeron]

While the new Desktop v2 layout is beautiful and welcoming for new users, the classic interface—with its side-by-side split panels, visible file trees, and native file referencing—remains an incredibly production-grade, highly efficient setup for daily coding. This feature is designed to elevate this workflow.

Workspace Safety and Cleanup

• Safety Safeguards: Accidental deletion is a major risk when managing dozens of sessions. Adding a native sidebar delete action complete with a clear confirmation dialog ensures developers can safely keep their workspace clean without the risk of losing valuable code history.