Population gate audit: static overnight gap everywhere + full band

The 2026-07-08 audit (owner: "figure out if there is some kind of logic
or audit issue") found BOTH entry paths feeding the population gate the
WRONG gap. The fast path used the trigger book's dynamic gap (latest
price vs prev close), so intraday rallies masqueraded as gappers: TVRD
(6.0% true gap), SKIN (2.2%, filled at $0.98), JLHL (4.3%) all traded
outside the validated population. The slow path used max(gap, intraday)
with "open" taken from the first lookback-window bar, and had no upper
band at all — dead-band names SEER (38.6%) and IOTR (40.7%) entered.

Fixes: candidates carry gap_open_pct (session open vs prev close);
trigger eligibility + submit_breakout_now use it exclusively once the
session is open; _population_reject now implements the full validated
band (10-35% OR volume-verified >=150% squeeze, $1-20 price band) for
both paths; evaluator gap uses the session open; signals carry
relative_volume for squeeze verification. Plus momentum-testpg.service
so the test-isolation Postgres survives reboots.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

research/ingestion/signals.py

@@ -18,10 +18,11 @@ SCANNER_VERSION = "gapper-v2"
 class GapperCandidate:
     symbol: str
     price: float
-    gap_pct: float
+    gap_pct: float               # DYNAMIC: latest close vs prev close (display/rank)
     cumulative_volume: int
     relative_volume: float
     vwap: float | None
+    prev_close: float | None = None   # for the STATIC overnight gap (open vs prev close)
     rank: int = 0
 
 
@@ -88,6 +89,7 @@ def scan_gappers(
                 GapperCandidate(
                     symbol=symbol,
                     price=float(close),
+                    prev_close=float(prev_close),
                     gap_pct=gap_pct,
                     cumulative_volume=int(cum_volume),
                     relative_volume=rvol,