Remove TracerTask

Its brewpi.mat output had no consumer - the GUI never subscribed to the
'Tracer' channel, and SudLogTask's run-scoped JSON logs now cover the same
sensor/heater/tc data for actual analysis. Drop the task, its DT_TASK_TRACER
interval, and the wiring in server/brewpi.py.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DkkuG48uHFCGKe6dPSERFk

tasks/sud_log.py

@@ -21,9 +21,10 @@ class SudLogTask(ATask):
 	power_eff - see client/brewpi_gui.py's PlotCanvas.sample()), plus
 	the forecast curve it's compared against (tasks/sud.py's SudTask.
 	forecast_t/forecast_theta), for the whole duration of a Sud run -
-	for later offline analysis. One pair of JSON files per run, not the
-	ever-growing, continuously-rewritten .mat tasks/tracer.py's
-	TracerTask already produces independently of any Sud run.
+	for later offline analysis. One pair of JSON files per run, scoped
+	to that run alone - unlike a continuously-rewritten trace file that
+	keeps growing independently of whether a Sud run is even in
+	progress.
 
 	A fresh, uniquely-named pair of logs starts the moment a run
 	actually starts (Sud.state leaves IDLE/DONE) and is written out