feat(interface): show resume hint on user-initiated exit

When the user shuts down a run (Ctrl+C in CLI, Ctrl+Q / quit dialog
in TUI, or an uncaught exception during the scan), print a Rich
panel telling them the exact command to pick up where they left off:

    strix --run-name <run_name>

The panel only appears when ``strix_runs/<run_name>/bus.json``
exists — i.e. the scan registered at least the root agent and has
snapshot state worth resuming from. Suppressed when:

  * No run-name was assigned (Ctrl+C before sandbox bring-up).
  * The run dir doesn't exist or has no bus.json yet.

Implementation:

  * ``strix/interface/utils.py`` gains ``format_resume_hint(run_name)
    -> Panel | None``.
  * ``cli.py`` calls it in the SIGINT/SIGTERM/SIGHUP handler before
    ``sys.exit(1)``, and in the ``except Exception`` arm before the
    re-raise.
  * ``tui.py:run_tui`` calls it in a ``finally`` after
    ``app.run_async()`` so the hint lands on the real terminal once
    Textual has restored it (whether the user pressed Ctrl+Q,
    confirmed the quit dialog, or the run completed naturally).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

strix/interface/cli.py

@@ -21,6 +21,7 @@ from strix.telemetry.tracer import Tracer, set_global_tracer
 
 from .utils import (
     build_live_stats_text,
+    format_resume_hint,
     format_vulnerability_report,
 )
 
@@ -139,6 +140,10 @@ async def run_cli(args: Any) -> None:  # noqa: PLR0915
 
     def signal_handler(_signum: int, _frame: Any) -> None:
         tracer.cleanup()
+        hint = format_resume_hint(args.run_name)
+        if hint is not None:
+            console.print()
+            console.print(hint)
         sys.exit(1)
 
     atexit.register(cleanup_on_exit)
@@ -212,6 +217,10 @@ async def run_cli(args: Any) -> None:  # noqa: PLR0915
 
     except Exception as e:
         console.print(f"[bold red]Error during penetration test:[/] {e}")
+        hint = format_resume_hint(args.run_name)
+        if hint is not None:
+            console.print()
+            console.print(hint)
         raise
 
     if tracer.final_scan_result: