feat(interface): show resume hint on the existing exit panel

When a scan ends without calling ``finish_scan`` (Ctrl+C, TUI quit,
crash), ``display_completion_message`` now appends one extra line
inside the existing completion panel:

    Resume  strix --run-name <run_name>

Same ``dim``-label / coloured-value styling as the panel's ``Target``
and ``Output`` rows. Only rendered when ``scan_completed`` is False —
a finished scan doesn't need a resume nudge.

Triggers ``orchestration/scan.py``'s implicit-resume path on the next
invocation (presence of ``{run_dir}/bus.json`` is the trigger), so
the user gets back exactly where they left off — root + every
non-terminal subagent's full LLM history, bus topology, prior
findings.

Covers both ``run_cli`` and ``run_tui`` paths since
``display_completion_message`` is called from ``main()`` regardless
of which front-end ran.

strix/interface/main.py

@@ -464,6 +464,14 @@ def display_completion_message(args: argparse.Namespace, results_path: Path) ->
     results_text.append(str(results_path), style="#60a5fa")
     panel_parts.extend(["\n", results_text])
 
+    if not scan_completed:
+        resume_text = Text()
+        resume_text.append("\n")
+        resume_text.append("Resume", style="dim")
+        resume_text.append("  ")
+        resume_text.append(f"strix --run-name {args.run_name}", style="#22c55e")
+        panel_parts.extend(["\n", resume_text])
+
     panel_content = Text.assemble(*panel_parts)
 
     border_style = "#22c55e" if scan_completed else "#eab308"