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/utils.py

@@ -1449,37 +1449,3 @@ def validate_config_file(config_path: str) -> Path:
         sys.exit(1)
 
     return path
-
-
-def format_resume_hint(run_name: str | None) -> Panel | None:
-    """Tell the user how to resume the current run, if it persisted state.
-
-    Returns a Rich :class:`Panel` ready to ``console.print`` when
-    ``strix_runs/<run_name>/bus.json`` exists (i.e. the scan registered
-    at least the root agent and has snapshot state to resume from).
-    Returns ``None`` when there's nothing to resume — e.g. the user hit
-    Ctrl+C before sandbox bring-up, or no run-name was assigned yet.
-
-    Mirrors the auto-resume contract in ``orchestration/scan.py``:
-    re-running with the same ``--run-name`` picks up where this scan
-    left off; deleting ``strix_runs/<run_name>/`` forces a fresh start.
-    """
-    if not run_name:
-        return None
-    run_dir = Path("strix_runs") / run_name
-    if not (run_dir / "bus.json").exists():
-        return None
-
-    text = Text()
-    text.append("Run paused. Resume any time with:\n\n", style="white")
-    text.append(f"  strix --run-name {run_name}\n", style="bold #60a5fa")
-    text.append("\nOr delete ", style="dim")
-    text.append(f"strix_runs/{run_name}/", style="bold dim")
-    text.append(" to start fresh.", style="dim")
-    return Panel(
-        text,
-        title="[bold white]STRIX",
-        title_align="left",
-        border_style="#60a5fa",
-        padding=(1, 2),
-    )