Fix elapsed showing --:-- at DONE, and energy not reset on restart

sud_elapsed_seconds is intentionally reset to None once a run leaves
a running state (it gates the forecast plot's dynamic-vs-static view
switch) - but the status bar/Progress tab reused it too, so they lost
the final total exactly when it mattered most: right as the run
finished. Added sud_elapsed_last, which only ever gets overwritten by
a real 'Elapsed' push and is reset on a fresh Start/Load, for those
two displays to use instead.

Separately, a fresh Start (restarting an already-loaded, now IDLE/
DONE schedule) never sent a new Load, so SudTask's energy bookkeeping
- previously only reset in the Load handler - kept showing the
previous run's banked totals until each step was revisited. Now also
reset on a fresh Start (not a Pause->resume, which should keep it).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019qvu5giu7gvRCyEWzf2Vpx

tasks/sud.py

@@ -430,6 +430,14 @@ class SudTask(ATask):
 				# whatever temperature existed back at Load (time passed,
 				# possibly manual heating in between).
 				fresh_start = self.sud.state in (SudState.IDLE, SudState.DONE)
+				if fresh_start:
+					# Belongs to the run that just ended (Stop, or running
+					# the schedule through to DONE), not the one about to
+					# begin - a Pause->resume (fresh_start False) keeps it,
+					# same as the forecast above.
+					self.energy_step_accum_j = 0.0
+					self.energy_by_step = {}
+					self._energy_index = None
 				self.sud.start()
 				if fresh_start:
 					asyncio.create_task(self.send_forecast(self.sud.save()))