backfill: overlay bw_report onto Event before DB upsert

Mirror what the ingest path does: BW's reported peaks (and sample_rate
/ record_time) take precedence over codec output where present.

Without this, --force backfill silently overwrites bw_report-overlaid
DB columns with codec-derived peaks.  Wrong for events where the codec
doesn't fully decode (waveform walker edge cases on SP0/SS0/SV0-style
events, histogram byte[5]!=0 sub-format that isn't yet RE'd), producing
PVS=0 on real high-amplitude events.  Bit on prod 2026-05-22 with
three top-10 waveform events ending up at PVS=0 (rolled back same day,
this fix is the proper resolution).

New helper minimateplus.event_file_io.apply_bw_report_dict_to_event
operates on the projected sidecar dict shape (the structure
_bw_report_to_dict produces, which is what gets preserved in the
sidecar).  Mirrors apply_report_to_event's semantics: only writes
fields where bw_report has a non-None value, no-ops cleanly on
empty / None input.

Dev validation against prod snapshot:
  pre  : 1839.7315 pvs_sum   356 events with DB PVS ≠ sidecar bw_report
  post : 2016.4902 pvs_sum     2 events still mismatched (both have NULL
                                timestamp + duplicate rows, edge case)

Both edge-case events DO get the correct value written by the new
backfill — their stale rows from prior backfills remain because
UNIQUE(serial, timestamp) doesn't fire on NULL.  Separate dedup
cleanup needed for those 2 events (0.014% of corpus); not blocking.

Backfill remains idempotent + bw_report preservation still passes
(0 WIPED, 0 CHANGED on the 3rd consecutive run).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

minimateplus/event_file_io.py

@@ -254,6 +254,60 @@ def apply_report_to_event(event: Event, report: BwAsciiReport) -> None:
         event.rectime_seconds = report.record_time_s
 
 
+def apply_bw_report_dict_to_event(event: Event, bw_report: dict) -> None:
+    """Mirror of ``apply_report_to_event`` for the projected sidecar
+    dict shape (as produced by ``_bw_report_to_dict``).
+
+    Why this exists
+    ───────────────
+    The ingest path holds a live ``BwAsciiReport`` parsed straight from
+    the ``_ASCII.TXT`` and uses ``apply_report_to_event`` to overlay
+    device-authoritative peaks onto the codec output before insert.
+
+    The backfill path doesn't have the original ``.TXT`` (it's not
+    retained in the waveform store), but it does have the preserved
+    ``bw_report`` block from the sidecar — which contains the same
+    projected fields.  Re-overlaying those during a backfill keeps the
+    DB peak columns aligned with what BW reports rather than letting
+    the codec output (which may be incomplete for unhandled formats or
+    walker edge cases) win by default.
+
+    No-ops cleanly when ``bw_report`` is ``None``, empty, or missing
+    any particular sub-field — only fields with a concrete value get
+    written.  Mirrors ``apply_report_to_event``'s "report wins where
+    present" semantics.
+    """
+    if not bw_report:
+        return
+    if event.peak_values is None:
+        event.peak_values = PeakValues()
+    pv = event.peak_values
+
+    peaks = bw_report.get("peaks") or {}
+    tran = (peaks.get("tran") or {}).get("ppv_ips")
+    vert = (peaks.get("vert") or {}).get("ppv_ips")
+    long = (peaks.get("long") or {}).get("ppv_ips")
+    if tran is not None: pv.tran = tran
+    if vert is not None: pv.vert = vert
+    if long is not None: pv.long = long
+    vs_ips = (peaks.get("vector_sum") or {}).get("ips")
+    if vs_ips is not None:
+        pv.peak_vector_sum = vs_ips
+
+    mic = bw_report.get("mic") or {}
+    pspl = mic.get("pspl_dbl")
+    if pspl is not None and pspl > 0:
+        pv.micl = _dbl_to_psi(pspl)
+
+    rec = bw_report.get("recording") or {}
+    sr = rec.get("sample_rate_sps")
+    if sr:
+        event.sample_rate = sr
+    rt = rec.get("record_time_s")
+    if rt is not None:
+        event.rectime_seconds = rt
+
+
 def _project_info_to_dict(pi: Optional[ProjectInfo]) -> dict:
     if pi is None:
         return {