Millennia eV: status snapshot + preserve init error

Two small gaps on the eV driver that pushed work into downstream callers:

* doInitializeDevice caught the failure and raised a bare
  PhysicalDevice.UnableToInitialize(), discarding the underlying
  serial error. Callers could no longer tell a busy port ("[Errno 16]
  Resource busy") from a missing one. Now re-raises
  UnableToInitialize(error) from error so the cause is preserved.

* MillenniaEv25Device did not override doGetStatusUserInfo(), so the
  base returned None and PhysicalDevice.startBackgroundStatusUpdates()
  posted empty status notifications for the eV. Added an override
  returning {power, isLaserOn, isShutterOpen} — a one-call snapshot for
  background monitoring and for GUI polling.

Adds a debug-device test for the status snapshot.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K6LVhfM3d9CcJdkuSMMqag

Author: dccote

hardwarelibrary/sources/millennia.py

@@ -80,10 +80,13 @@ def doInitializeDevice(self):
             self.port = SerialPort(portPath=self.portPath)
             self.port.open(baudRate=self.defaultBaudRate)
             self.readIdentity()
-        except Exception:
+        except Exception as error:
             if self.port is not None and self.port.isOpen:
                 self.port.close()
-            raise PhysicalDevice.UnableToInitialize()
+            # Preserve the underlying error (e.g. pyserial's "[Errno 16]
+            # Resource busy") so callers can tell a busy port from a missing
+            # one instead of seeing a bare, info-less UnableToInitialize.
+            raise PhysicalDevice.UnableToInitialize(error) from error
 
     def readIdentity(self):
         # The eV identifies via the SCPI-style *IDN? query. The ?IDN form in
@@ -197,6 +200,20 @@ def doGetPower(self) -> float:
         # token.
         return float(self.queryString("?P").split()[0])
 
+    # Status snapshot
+
+    def doGetStatusUserInfo(self) -> dict:
+        # Single-call snapshot for PhysicalDevice.startBackgroundStatusUpdates()
+        # (posted as PhysicalDeviceNotification.status) and for GUI polling: the
+        # output power plus the diode (emission) and shutter states. Without this
+        # override the base returns None, so the monitoring loop posts nothing
+        # useful for the eV.
+        return {
+            "power": self.doGetPower(),
+            "isLaserOn": self.doGetOnOffState(),
+            "isShutterOpen": self.doGetShutterState(),
+        }
+
 
 class DebugMillenniaEv25Device(MillenniaEv25Device):
     classIdVendor = 0xFFFF

hardwarelibrary/tests/testMillennia.py

@@ -104,6 +104,15 @@ def testShutterIsIndependentOfOnOff(self):
         self.assertFalse(self.laser.isLaserOn())
         self.assertTrue(self.laser.isShutterOpen())  # off, shutter unchanged
 
+    def testStatusUserInfoSnapshotsPowerOnOffAndShutter(self):
+        self.laser.setPower(7.5)
+        self.laser.turnOn()
+        self.laser.openShutter()
+        self.assertEqual(
+            self.laser.doGetStatusUserInfo(),
+            {"power": 7.5, "isLaserOn": True, "isShutterOpen": True},
+        )
+
 
 class TestMillenniaEv25Device(unittest.TestCase):
     def setUp(self):