feat: always write a fixed-name copy of server/sud logs, use .json for sud logs

Alongside the dated log files, ServerLogTask/SudLogTask now also write
(and overwrite) a fixed-name copy on every write() - logs/log_latest.json
and logs/log_latest_sud.json - so a dashboard/tail-style consumer can
point at one unchanging path instead of tracking the current run's
timestamped filename.

Also switches SudLogTask's own dated/latest filenames from .log to .json,
matching what they've always actually contained. This incidentally fixes
utils/analyze_log.py's two-argument CLI form, which already assumed a
.json extension for sud logs.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JFDeoTKBDkXRhPfnyDEoBt

tasks/server_log.py

@@ -89,6 +89,13 @@ class ServerLogTask(ATask):
 	def _filename(self):
 		return 'log_{}.json'.format(self._run_id)
 
+	def _latest_filename(self):
+		"""Fixed (no-date) name written alongside the dated one on every
+		write() - always overwritten, so a dashboard/tail-style consumer
+		can point at one unchanging path instead of tracking the current
+		run's own timestamped filename."""
+		return 'log_latest.json'
+
 	def _extra_log_data(self):
 		"""Hook for subclasses (SudLogTask) to contribute additional keys
 		to write()'s output - see there."""
@@ -105,7 +112,6 @@ class ServerLogTask(ATask):
 			return
 		os.makedirs(self.path, exist_ok=True)
 		filename = self._filename()
-		path = os.path.join(self.path, filename)
 		log_data = {'Name': self._log_name()}
 		if self.dt is not None:
 			log_data['dt'] = self.dt
@@ -122,6 +128,11 @@ class ServerLogTask(ATask):
 			log_data['PlantParams'] = self._param_events
 		log_data.update(self._extra_log_data())
 		log_data['Samples'] = self._samples
-		with open(path, 'w') as f:
-			json.dump(log_data, f, indent='\t')
+		# Written to both the dated filename (this run/session's own
+		# permanent record) and a fixed, always-overwritten one (see
+		# _latest_filename()) - same content, so a consumer wanting
+		# "whatever's most current" never has to track the dated name.
+		for name in (filename, self._latest_filename()):
+			with open(os.path.join(self.path, name), 'w') as f:
+				json.dump(log_data, f, indent='\t')
 		print('Server log: wrote {} samples to {}'.format(len(self._samples), filename))