fix return-value/deprecated API bugs, accumulation lock leaks, code cleanup

- raise instead of silent None for unsupported operands and empty negation
- validate before acquiring lock in Accumulation operators (no RLock leak)
- Accumulation._copy_provenance helper, ADC_Result._copy_metadata for all result paths
- shared _sandbox_stdout_redirect contextmanager for sandboxed scripts
- TemperatureMonitor dead code removal (gtk helper, traceback, unused properties)
- new unit tests incl. lock-freedom regression test
- gitignore sphinx generated doc/_autosummary/ and doc/damaris/

src/damaris/tools/eurotherm.py

@@ -1,5 +1,6 @@
 import serial
 import re
+import time
 import operator
 from functools import reduce
 
@@ -57,21 +58,22 @@ class Eurotherm(TemperatureController):
 	def send_read_param(self, param):
 		self.s.write(EOT + self.device + param + ENQ)
 
-	def read_param(self, param):
-		self.s.flushInput()
-		self.send_read_param(param)
-		answer = self.s.read(self._expect_len)
-		m = reply_pattern.search(answer)
-		if m is None:
-			# Reading _expect_len bytes was not enough...
-			answer += self.s.read(200)
+	def read_param(self, param, retries=3, retry_delay=0.05):
+		for attempt in range(retries):
+			self.s.flushInput()
+			self.send_read_param(param)
+			answer = self.s.read(self._expect_len)
 			m = reply_pattern.search(answer)
-		if m is not None:
-			self._expect_len = len(answer)
-			return m.group(1)
-		else:
-			print("received:", repr(answer))
-			return None
+			if m is None:
+				answer += self.s.read(200)
+				m = reply_pattern.search(answer)
+			if m is not None:
+				self._expect_len = len(answer)
+				return m.group(1)
+			if attempt < retries - 1:
+				time.sleep(retry_delay)
+		print("received:", repr(answer))
+		return None
 
 	def write_param(self, mnemonic, data):
 		if len(mnemonic) > 2:
@@ -128,6 +130,14 @@ class Eurotherm(TemperatureController):
 		"""Set target temperature in Celsius."""
 		return self.write_param('SL', str(temperature))
 
+	def check_connection(self) -> bool:
+		"""Check if the Eurotherm device is connected and responsive."""
+		try:
+			result = self.read_param('PV')
+			return result is not None
+		except Exception:
+			return False
+
 	def close(self):
 		"""Close the serial connection."""
 		if hasattr(self, 's') and self.s is not None: