Simplify single-test to match vendor capture exactly

Remove send_test_config() call - vendor software doesn't send 8C 2B for
each single test, only when changing modes. Remove set_integration_time()
from spectrometer.py - vendor doesn't send 8C 01 either.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

hpcs6500.py

@@ -456,12 +456,11 @@ class HPCS6500:
 
         return result
 
-    def take_single_reading(self, auto_psu=False):
+    def take_single_reading(self):
         """Trigger a single measurement matching the vendor's single-test flow.
-        Sends test config, then stop to trigger a one-shot reading, waits for
-        data, reads it, then resets.
-        If auto_psu=True, the device handles PSU on/off automatically."""
-        self.send_test_config(auto_psu=auto_psu)
+        Sends stop to trigger a one-shot reading, waits for data, reads it,
+        then resets. The device should be in single-test mode (configured via
+        vendor software UI or send_test_config())."""
         self.stop_measurement()
 
         if not self.wait_for_data(timeout=30.0):

spectrometer.py

@@ -16,7 +16,6 @@ def measure():
     dev = HPCS6500(port)
     try:
         dev.identify()
-        dev.set_integration_time(0)  # auto
         reading = dev.take_single_reading()
     finally:
         dev.close()