audit: round three on the port — the hardware scan check fails soft

A rig hiccup mid-walk records the scan check as failed and lets the suite
continue, matching its siblings' envelope; a nonexistent --port path
reports as an error instead of a traceback.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pureboot/pureboot.py

@@ -1600,7 +1600,7 @@ def main():
 if __name__ == "__main__":
     try:
         main()
-    except Error as error:
+    except (Error, OSError) as error:
         print(f"error: {error}", file=sys.stderr)
         sys.exit(1)
     except KeyboardInterrupt:

tools/pbhw.py

@@ -82,22 +82,26 @@ class Suite:
         on silicon."""
         module = pbrig.load_pureboot(self.rig.d.pureboot)
         found = None
-        for pct in module.scan_ratios():
+        try:
-            rate = module.scan_rate(self.rig.d.baud, pct)
+            for pct in module.scan_ratios():
-            self.rig.reset()
+                rate = module.scan_rate(self.rig.d.baud, pct)
-            try:
+                self.rig.reset()
-                port = module.Port(self.rig.d.port, rate)
+                try:
-            except module.Error as error:
+                    port = module.Port(self.rig.d.port, rate)
-                self.check("scan opens every probe rate", False, f"{rate} Bd: {error}")
+                except module.Error as error:
-                return
+                    self.check("scan opens every probe rate", False, f"{rate} Bd: {error}")
-            try:
+                    return
-                module.Loader(port).connect(min(self.rig.d.wait, 6.0))
+                try:
-                found = pct
+                    module.Loader(port).connect(min(self.rig.d.wait, 6.0))
-                break
+                    found = pct
-            except module.Error:
+                    break
-                continue
+                except module.Error:
-            finally:
+                    continue
-                port.close()
+                finally:
+                    port.close()
+        except Exception as error:  # noqa: BLE001 — a rig hiccup is a result
+            self.check("scan walks the probe ladder", False, str(error)[:70])
+            return
         self.check("scan finds the board's rate", found is not None,
                    "no probe answered" if found is None else f"{found:+d} % of {self.rig.d.baud} Bd")