SAFETY-90: the peak guard goes on after a P1 meter gap

A meter gap past meter_max_age_s left seconds the quarter average never
counted, so the guard was blind for the rest of the quarter (rig case 7b:
3964.8 W against a 3450 W aim). Once readings are back, the missed seconds
now count at the higher of the limit and the import seen just before and
just after the gap with the batteries at 0 W (peakguard.gap_w/fill_gaps);
the gap's first meter_max_age_s is topped up to that too. Seconds before
the add-on's first reading count at the aim, and the page says part of the
period was not measured (EN/NL). The bill record is unchanged; no option.

DECISIONS/SAFETY-90-peak-guard-after-a-gap.md, test_safety90.py.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

goodwe_controller/app/peakguard.py

@@ -183,6 +183,8 @@ guard passes its own tests while being switched off:
     record). Those seconds make the projection read LOW, which is the
     under-guarding direction. The threshold is `max_hold_s` itself - the point
     p1.py already stops trusting a held sample - not a new number.
+    SAFETY-90: once readings are back, main.py counts those seconds
+    (`fill_gaps()`), so this holds only while the gap lasts.
 
   * FROZEN. SAFETY-18's conjunction, evaluated through `freeze.looks_frozen()`
     rather than re-written here. A frozen meter is the worst case of all: the
@@ -599,6 +601,57 @@ def blindness(projection, max_hold_s, frozen: bool) -> str | None:
     return None
 
 
+# SAFETY-90. Seconds of uncounted time below which nothing is filled: float
+# noise between the averager's sums and the wall clock, never a real gap.
+GAP_TOL_S = 1e-3
+
+
+def gap_w(ceiling_w, *seen_w) -> float:
+    """SAFETY-90: the watts a meter gap is counted at. The highest of the
+    limit and `seen_w`, the import with the batteries at 0 W (grid + their
+    discharge) just before and just after the gap; None entries are skipped.
+    DECISIONS/SAFETY-90-peak-guard-after-a-gap.md."""
+    return max([float(ceiling_w)] + [float(w) for w in seen_w if w is not None])
+
+
+def fill_gaps(projection, *, tail_s, max_hold_s, unseen_s, gap_w, unseen_w,
+              held_ws=0.0):
+    """SAFETY-90: `projection` with the seconds the averager did not count
+    (a meter gap past `max_hold_s`) counted at `gap_w`, and those from before
+    this run's first reading (`unseen_s`) at `unseen_w`. `held_ws` is added
+    too: what the gap's first `max_hold_s`, credited at the reading before
+    it, lacks to reach `gap_w`. Returns
+    `(projection, gap seconds filled, unseen seconds filled)`.
+
+    `tail_s` is the age of the held reading: up to `max_hold_s` of it is left
+    as before (the averager credits it once the next reading lands). Past
+    that the gap is still open, nothing is filled and `blindness()` answers
+    as before. DECISIONS/SAFETY-90-peak-guard-after-a-gap.md."""
+    if projection.block_start is None or max_hold_s is None:
+        return projection, 0.0, 0.0
+    wall = float(projection.elapsed_s)
+    tail = min(max(0.0, float(tail_s)), wall)
+    if tail > float(max_hold_s):
+        return projection, 0.0, 0.0
+    covered = wall - uncovered_s(projection)
+    missing = wall - covered - tail
+    if missing <= GAP_TOL_S:
+        missing = 0.0
+        if held_ws <= 0.0:
+            return projection, 0.0, 0.0
+    unseen = min(missing, max(0.0, float(unseen_s)))
+    gap = missing - unseen
+    add_ws = gap * float(gap_w) + unseen * float(unseen_w) + float(held_ws)
+    done = covered + missing
+    return (replace(
+        projection,
+        projected_w=float(projection.projected_w) + add_ws / QUARTER_S,
+        elapsed_w=((float(projection.elapsed_w) * covered + add_ws) / done
+                   if done > 0.0 else float(projection.elapsed_w)),
+        covered_frac=(done / wall if wall > 0.0
+                      else float(projection.covered_frac))), gap, unseen)
+
+
 def discharge_permitted(soc, soc_floor) -> str | None:
     """SAFETY-24. May the guard size a forced discharge, or why may it not?