Add a keyboard shortcut to delete a session directly from the session list

Problem

In the desktop app, deleting a session from the sidebar is a two-step process: open the session's "⋮" context menu first, then press D inside that menu to trigger the delete confirmation.

This is fine for deleting a single session, but it adds up when cleaning up several sessions in a row (e.g. clearing out old experimental sessions, pruning a long history list) — every single deletion requires re-opening the menu before the shortcut can even be used.

Current behavior

1. Hover/focus a session row in the sidebar.
2. Click (or otherwise open) the "⋮" menu for that row.
3. Press D (or select "Delete") inside the opened menu.
4. Confirm in the delete confirmation modal.

Proposed behavior

Let the currently focused/hovered session row respond to the delete shortcut (e.g. D) directly, without requiring the "⋮" menu to be opened first. This would collapse steps 2–3 above into a single keypress on the row itself.

The existing confirmation modal (step 4) should stay exactly as-is — the goal is to skip the extra menu-opening step, not to remove the safety check that prevents accidental deletion.

Alternative: repurpose the existing (effectively unused) close-session shortcut

There is already a Cmd+W / Ctrl+W shortcut intended to close the current session. In practice, though, it doesn't actually close the session — it behaves the same as starting a new session, so today it isn't doing the job its name suggests. Rather than introducing a brand-new shortcut, this existing (and currently redundant) shortcut could instead be repurposed to trigger the delete-session flow described above (still going through the confirmation modal).

Non-goals

• Not asking to remove or change the "⋮" menu itself — it should keep working as an alternative path for mouse-first users.
• Not asking to skip or weaken the confirmation modal.
• Not asking for multi-select/bulk delete — this is about removing friction from the existing single-session delete flow.