[FEATURE] Desktop: replace the delete-session confirmation modal with a recoverable "Recently deleted" view

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

Deleting a session in the desktop sidebar requires confirming a modal every time. The modal is there to prevent accidental loss, but it charges that cost on every delete to protect against the rare mistake — so pruning a history list means dismissing one modal per session.

Confirmation dialogs are also weak protection in this position. When a dialog appears on every single delete, it gets clicked through reflexively, so it stops being a real check and just becomes friction. The result is a delete action that is both annoying to use and not actually safe.

Proposed Solution

Make delete instant and undoable rather than slow and irreversible — the pattern used by Finder, Gmail, and Photos:

1. Deleting a session removes it from the sidebar immediately, with no modal.
2. An undo affordance appears briefly — a toast with "Undo", and/or Cmd+Z.
3. Deleted sessions move to a "Recently deleted" view where they can be restored, with permanent removal available explicitly (a "Delete permanently" action, automatic expiry after N days, or both).

Most of the machinery for this seems to exist already. Sessions carry an isArchived flag and the session list can be queried with archived entries included, so there is already a notion of "present but hidden from the default view." Delete also does not appear to remove the transcript from disk: in one project directory I have 11 .jsonl transcripts under ~/.claude/projects/<encoded-dir>/ but only 2 sessions visible in the sidebar. The data needed for a restore is already on disk — what's missing is a UI path back to it.

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

Other

Use Case Example

1. I finish a week of work across several short-lived sessions — a few experiments, a couple of one-off questions, some that went nowhere.
2. I want to clear them out so the sidebar shows only work I'm still tracking.
3. Today each removal is: open the row's "⋮" menu, choose Delete, confirm the modal. Six sessions means six modals, and if I misjudge one there is no way back.
4. With this change I delete them in six keystrokes, and if I remove the wrong one I hit Undo or pull it out of "Recently deleted."

Additional Context

_No response_