fix: allow closing last session tab and restore DevTools shortcut

Closing the sole remaining non-welcome tab now resets to welcome; enable Tauri devtools, menu/shortcut toggle, and copy release artifacts from CARGO_TARGET_DIR.

Co-authored-by: Cursor <cursoragent@cursor.com>

src-tauri/Cargo.toml

@@ -31,7 +31,7 @@ sha2 = "0.10"
 hmac = "0.12"
 portable-pty = "0.9"
 serialport = { version = "4.8", default-features = false, features = ["libudev"] }
-tauri = { version = "2.8", features = [] }
+tauri = { version = "2.8", features = ["devtools"] }
 tauri-plugin-deep-link = "2"
 tauri-plugin-single-instance = "2"
 thiserror = "2.0"