feat: responsive pause/stop, non-blocking update with progress bar, delete saved sessions (1.5.0)

- carve: check cancellation inside chunks and per hit; reassembly stage is cancellable
- status exposes `stopping`; UI shows "Pausing…" immediately
- Tauri update commands run off the UI thread; download percentage reported
- delete autosaved sessions manually (one/all) and by retention setting
- chore(release): 1.5.0

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -4,6 +4,16 @@
 
 Format based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); versions follow SemVer.
 
+## [1.5.0] - 2026-11-03
+
+### Added
+- **Update progress bar.** The in-app update shows a real download percentage bar followed by the verify/install/restart phases.
+- **Delete saved sessions.** Each autosaved session in the sidebar has a delete button, plus a "delete all" button. Settings gained "Delete autosaved sessions after" (never, 7, 30 or 90 days), applied on startup. Sessions open in the app are never removed automatically.
+
+### Fixed
+- **Updating no longer freezes the app.** The update check and install ran on the UI thread; they now run in the background.
+- **Pause and Stop respond right away.** The signature scan only checked for the request once per 8 MiB block; it now checks continuously, and the UI shows "Pausing…" immediately.
+
 ## [1.4.0] - 2026-11-03
 
 ### Added