feat(bw-report): normalise operator-field label variants

Blastware writes the operator-supplied fields with different label
spellings across firmware versions and recording modes — most
notably "Seis. Location" on histogram exports vs "Seis Loc:" on
waveform exports.  Previous parser only matched the latter, so
every histogram event silently lost its sensor_location field.

Replace the four hardcoded `key.rstrip(":") == "X"` branches with
a single `_OPERATOR_LABEL_MAP` dispatch table keyed by normalised
label (lowercase, trailing colon/period stripped, internal
whitespace collapsed).  Adds these variants on day 1:

  project:         "Project:" / "Project"
  client:          "Client:"  / "Client"
  operator:        "User Name:" / "User Name"
  sensor_location: "Seis Loc:" / "Seis. Location" / "Seis Location"
                 / "Sensor Location" / "Seis Loc"

To absorb future BW label drift, add a one-line dict entry — no
new elif branch.

14 new tests cover:
  - Each label variant routes to the correct field (parametrised)
  - Case-insensitive matching ("seis loc" / "SEIS LOC" / "SeIs LoC")
  - Whitespace-collapse ("Seis  Loc" with double-space)
  - End-to-end parse of a real histogram fixture from
    example-events/histogram/ — sensor_location ('Loc #1 - 2652 Hepner...')
    populates correctly even though the file uses "Seis. Location"

Total bw_ascii_report tests: 19 → 33.  Full SFM suite still green
(69 passed, 44 skipped — pre-existing skips for h5py-dep tests).

Pairs with series3-watcher v1.5.4 (which fixes the filename pairing
so histograms actually reach this parser in the first place).

minimateplus/bw_ascii_report.py

@@ -265,6 +265,61 @@ def _parse_monitor_ts(s: str) -> Optional[datetime.datetime]:
         return None
 
 
+# ── Operator-field label normalisation ──────────────────────────────────────
+#
+# BW has used different label spellings across versions and recording
+# modes for the same operator-supplied fields:
+#
+#   project:         "Project:" / "Project"
+#   client:          "Client:"  / "Client"
+#   operator:        "User Name:" / "User Name"
+#   sensor_location: "Seis Loc:" / "Seis. Location" / "Seis Location"
+#                  / "Sensor Location"
+#
+# Per user feedback ("the tags themselves dont matter a ton, what
+# matters is the field"), we normalise labels at lookup time so the
+# value-extraction works regardless of which spelling BW happens to
+# emit on a given machine.
+#
+# To add a new variant: edit `_OPERATOR_LABEL_MAP` — single source of
+# truth.  Keys are normalised forms (lowercase, trailing colon and
+# period stripped, internal whitespace collapsed); values are
+# attribute names on `BwAsciiReport`.
+
+_OPERATOR_LABEL_MAP = {
+    # project
+    "project":          "project",
+    # client
+    "client":           "client",
+    # operator
+    "user name":        "operator",
+    # sensor location — most variants of "Seis*" + "Sensor Location"
+    "seis loc":         "sensor_location",
+    "seis. loc":        "sensor_location",
+    "seis. location":   "sensor_location",
+    "seis location":    "sensor_location",
+    "sensor location":  "sensor_location",
+}
+
+
+def _normalise_label_for_lookup(key: str) -> str:
+    """Normalise a label for the operator-field lookup.
+
+    Strips a trailing colon and/or period, collapses internal
+    whitespace runs, and lowercases.  So all of:
+
+      "Seis Loc:"
+      "Seis. Location"
+      "seis  location"
+      "Sensor Location"
+
+    map to canonical forms in `_OPERATOR_LABEL_MAP`.
+    """
+    s = key.strip().rstrip(":").rstrip(".").strip()
+    s = _KEY_NORMALISE_RE.sub(" ", s)
+    return s.lower()
+
+
 # ─────────────────────────────────────────────────────────────────────────────
 # Top-level parser
 # ─────────────────────────────────────────────────────────────────────────────
@@ -346,12 +401,14 @@ def parse_report(text: Union[str, bytes], *, parse_samples: bool = False) -> BwA
             report.calibration_date, report.calibration_by = _parse_calibration(value)
         elif key == "Units":                report.units = value
 
-        # Project labels in BW carry their own trailing colon — after
-        # _normalise_key we just strip it for matching.
-        elif key.rstrip(":") == "Project":  report.project = value
-        elif key.rstrip(":") == "Client":   report.client = value
-        elif key.rstrip(":") == "User Name":report.operator = value
-        elif key.rstrip(":") == "Seis Loc": report.sensor_location = value
+        # Operator-supplied labels (Project / Client / User Name /
+        # Seis Loc) — BW writes these with assorted spellings across
+        # firmware versions and recording modes (e.g. "Seis Loc:" on
+        # waveform exports vs "Seis. Location" on histogram exports).
+        # The label normaliser absorbs all known variants; see
+        # `_OPERATOR_LABEL_MAP` above for the dispatch table.
+        elif (slot := _OPERATOR_LABEL_MAP.get(_normalise_label_for_lookup(key))):
+            setattr(report, slot, value)
 
         elif key == "Geo Range":            report.geo_range_ips = _parse_number(value)