SAFETY-79: CI fixes - MUTATION.md pointer, no key-taking helper, fixture sized on the aim

test_peakguard's over-limit fixture now sizes its load against
cap - margin, so the floor it asks for is exact wherever in the quarter
the suite runs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UBtqPrG1mDLXzTEBnhEkkV

goodwe_controller/test_peakguard.py

@@ -1175,7 +1175,9 @@ def wired_over_limit(db, want_floor_w, opts=None, store=None, batt_w=0.0,
             int(now.timestamp() // QUARTER_S) * QUARTER_S, timezone.utc)
         span = int((now - blk).total_seconds())
         remaining = max(1.0, QUARTER_S - (now - blk).total_seconds())
-        net_w = CAP_W + want_floor_w * remaining / QUARTER_S
+        # SAFETY-79: sized against what the guard aims at, cap - margin.
+        net_w = (CAP_W - ctl.peak_margin_w
+                 + want_floor_w * remaining / QUARTER_S)
         for i in range(0, span + 1, 5):
             ctl.p1.submit(sample(blk + timedelta(seconds=i), net_w))
         # ⚠️ AND ONE TELEGRAM AT `now` ITSELF. The averager credits a sample's