fix: 4 small surgical bugs

Salvages #23302 by @Bartok9. Four independent one-area fixes:

1. kanban boards delete alias now hard-deletes (not archives) — the
   alias didn't carry --delete, so getattr(args, 'delete', False)
   returned False. Detect boards_action=='delete' explicitly.
2. Gateway auto-title failures no longer leak as user-visible
   warnings — debug-log only since they're not actionable.
3. Background process completion notification snaps truncation to
   the next newline boundary, prepends a marker when content is
   dropped.
4. _cprint() schedules the run_in_terminal coroutine via
   asyncio.ensure_future so output isn't silently dropped from
   background threads (fixes #23185 Bug A). Skips the
   double-print fallback that would fire for mock paths.

cli.py

@@ -1835,13 +1835,26 @@ def _cprint(text: str):
     # prompt, prints, and redraws.  Fire-and-forget — if scheduling
     # fails we fall back to a direct print so the line isn't lost.
     def _schedule():
+        # run_in_terminal() may return either:
+        #   • a coroutine / Future (prompt_toolkit ≥ 3.0) — must be scheduled
+        #     via ensure_future so the coroutine is actually awaited; calling
+        #     it bare would leave it unawaited and silently drop the output
+        #     (fixes #23185 Bug A).
+        #   • None (some mocks / older PT builds) — just call the inner
+        #     function directly since PT already executed it synchronously.
+        # Do NOT fall back to a bare _pt_print when ensure_future raises,
+        # because run_in_terminal already invoked the lambda in that case
+        # (the mock path), which would double-print the line.
         try:
-            run_in_terminal(lambda: _pt_print(_PT_ANSI(text)))
+            import asyncio as _aio
+            import inspect as _inspect
+            coro = run_in_terminal(lambda: _pt_print(_PT_ANSI(text)))
+            if coro is not None and (_inspect.isawaitable(coro) or _inspect.iscoroutine(coro)):
+                _aio.ensure_future(coro)
+            # else: run_in_terminal ran the lambda synchronously; nothing more
+            # to do (double-scheduling would print twice).
         except Exception:
-            try:
-                _pt_print(_PT_ANSI(text))
-            except Exception:
-                pass
+            pass  # best-effort; the line may already have been printed
 
     try:
         loop.call_soon_threadsafe(_schedule)