MAINT-13 round 2: gate open when nothing holds the charge back; safety93 scenario restored

- gate_open is true with no price gate set up, in a cheap window, or while the
  pack is taking charge; the stall rule and timeout now work on a no-tariff site.
- reset the save timer on a phase change; exact 5 min gap-cap test.
- test_safety93: original timeout scenario kept (B finished) plus a case where a
  due B takes the slot after A's failure.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bdqr7PiaHcBnzPituu2yTC

goodwe_controller/DECISIONS/MAINT-13-full-pack-is-complete.md

@@ -61,15 +61,20 @@ as long as the wait lasts. The operator may also see the log lines.
 
 ## 3. The timeout counts only allowed time
 
-`Controller` passes `gate_open = self.cheap` (the same flag that lets the
-cheap-window charge floor apply). Only those ticks add to `open_min`; one tick
+`Controller._charge_gate_open()` says whether the pack may charge now. It is
+true when no price gate is set up (no price entities, no fixed tariff: nothing
+holds the charge back, and `cheap` is always false there), in a cheap window, or
+while the pack is really taking charge (battery power at or below -50 W, which is
+sun outside cheap hours). It is false only when a gate exists, is shut, and the
+pack is not charging; a pack asked for charge that delivers nothing then does not
+count, which is the case the clock cannot judge. Only open ticks add to `open_min`; one tick
 adds at most 5 min, so a gap (add-on down) adds nothing. The stall wait pauses
 while the gate is closed. The accounting is written to the state file at most
 every 5 min (`charge_track`); a restart loses at most that. A state file from
 before this change, or with no record for the current charge, starts from the
 wall-clock minutes so far, which is the old behaviour.
 
-**Backstop.** A site whose gate never opens (no tariff, no sun) would never time
+**Backstop.** A gated site whose gate never opens (no cheap hours, no sun) would never time
 out, so a charge also ends after 7 days of wall clock (`CHARGE_WALL_TIMEOUT_MIN`):
 complete at >= target - 3, a failure below.