feat(ui): confirm before closing a running ConPTY session

The tile's own X killed a live Claude session with no confirmation, unlike
the semantically similar Abandon-run action. Gate the close behind the same
ConfirmAsync mechanism, but only when Terminal.IsRunning -- a dead session
(StartError or exited-after-startup) still closes immediately since the X
there is pure cleanup.

src/ClaudeDo.Localization/locales/en.json

@@ -380,6 +380,7 @@
     "focusMode": "Focus",
     "overviewMode": "Overview",
     "closeSession": "Kill session",
+    "closeSessionConfirm": "End the running session? The Claude process will be aborted.",
     "conptyLaunchFailed": "Couldn't open interactive session: {0}",
     "conptyStarting": "Starting session…",
     "conptyExited": "Session ended (code {0}).",