feat: doctor reports bubblewrap availability

Adds a non-fatal bubblewrap check to the doctor command that reports whether
the bwrap binary is available. This is necessary for sandboxed sessions and
the check is displayed alongside other system requirement checks.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/hqt/cli.py

@@ -1,5 +1,6 @@
 import logging
 import os
+import shutil
 import subprocess
 import sys
 import traceback
@@ -105,7 +106,6 @@ def launch(inside_tmux: bool = False):
 @main.command()
 def doctor():
     """Check system requirements."""
-    import shutil
     from hqt.harnesses.registry import discover_harnesses
 
     tmux = shutil.which("tmux")
@@ -119,6 +119,11 @@ def doctor():
         click.echo(f"{name}: ✓")
     if not harnesses:
         click.echo("No harnesses found on PATH")
+    bwrap = shutil.which("bwrap")
+    if bwrap:
+        click.echo(f"bubblewrap: ✓ {bwrap}")
+    else:
+        click.echo("bubblewrap: ✗ not found — sandboxed sessions unavailable")
 
 
 @main.command(name="list")

tests/test_cli.py

@@ -0,0 +1,30 @@
+from unittest.mock import patch
+
+from click.testing import CliRunner
+
+from hqt import cli as cli_module
+from hqt.cli import main
+
+
+def _which(found: set[str]):
+    return lambda name: f"/usr/bin/{name}" if name in found else None
+
+
+def test_doctor_reports_bwrap_present():
+    """Test that doctor reports bubblewrap when present."""
+    # Patch the single shutil.which used by both cli and registry
+    with patch.object(
+        cli_module.shutil, "which", side_effect=_which({"tmux", "bwrap"})
+    ):
+        result = CliRunner().invoke(main, ["doctor"])
+    assert result.exit_code == 0
+    assert "bubblewrap: ✓" in result.output
+
+
+def test_doctor_reports_bwrap_missing():
+    """Test that doctor reports bubblewrap as missing when not present."""
+    # Patch the single shutil.which used by both cli and registry
+    with patch.object(cli_module.shutil, "which", side_effect=_which({"tmux"})):
+        result = CliRunner().invoke(main, ["doctor"])
+    assert result.exit_code == 0
+    assert "bubblewrap: ✗" in result.output