feat(import): Z-wafer CSV import button with result banner

- importZWaferCsv slot on FileBrowser — converts and adds to list
- SourcePanel: import icon button → FileDialog → importSummary banner
  (auto-dismisses after 5s, loads the converted file into streamController)
- wafer_map_item: showExtremes default → true

src/pygui/backend/data/file_browser.py

@@ -18,6 +18,7 @@ class FileBrowser(QObject):
     # ===== Change Signals =====
     filesChanged = Signal()
     currentDirectoryChanged = Signal()
+    importFinished = Signal(str, str)  # (new file path, or "" on failure; message)
 
     # ===== Lifecycle =====
     def __init__(self, parent: QObject | None = None) -> None:
@@ -110,6 +111,66 @@ class FileBrowser(QObject):
         self.filesChanged.emit()
         self._show_info(f"Saved metadata for:\n{csv_path.name}")
 
+    # ===== Z-Wafer Import =====
+    @Slot(str)
+    def importZWaferCsv(self, file_path: str) -> None:
+        """Port of C#'s ImportZWaferCSV (Form1.cs:1711): parse a raw Z-wafer
+        export, strip its leading row-index column, and write it into the
+        current directory as a normalized `{serial}-{timestamp}.csv`.
+
+        The timestamp is the source file's own acquisition date, not "now" —
+        deliberately, so re-importing the same source collides on purpose.
+        No fallback to wall-clock time: a file with no parseable acquisition
+        date still gets a deterministic (if degenerate) filename, so the
+        duplicate-import guard below still fires on a second attempt.
+        """
+        source_path = Path(file_path)
+        parser_data, _ = self._parser.parse(file_path)
+        if parser_data is None:
+            self.importFinished.emit("", f"Failed to parse CSV:\n{source_path.name}")
+            return
+
+        serial = parser_data.serial or "UNKNOWN"
+        new_filename = f"{serial}-{parser_data.date.strftime('%Y%m%d_%H%M%S')}.csv"
+        new_path = self._current_directory / new_filename
+
+        if new_path.exists():
+            self.importFinished.emit("", f"Already imported to:\n{new_filename}")
+            return
+
+        try:
+            data_rows = self._parser.parse_data_rows(file_path)
+        except Exception as exc:
+            self.importFinished.emit("", f"Failed to read data rows:\n{exc}")
+            return
+
+        try:
+            self._current_directory.mkdir(parents=True, exist_ok=True)
+            lines = [",".join(parser_data.csv_headers), *data_rows]
+            new_path.write_text("\n".join(lines) + "\n", encoding="utf-8")
+        except Exception as exc:
+            self.importFinished.emit("", f"Failed to write imported file:\n{exc}")
+            return
+
+        metadata = CSVFileMetadata(
+            wafer=serial,
+            date=CSVFileMetadata.format_date(parser_data.date),
+            chamber=parser_data.header.get("Chamber", ""),
+            notes=parser_data.header.get("Comments", ""),
+            filename=str(new_path),
+        )
+        try:
+            self._sidecar_path(new_path).write_text(
+                json.dumps(metadata.to_dict(), indent=4), encoding="utf-8"
+            )
+        except Exception as exc:  # pragma: no cover - defensive UI path
+            self._refresh_files(show_empty_message=False)
+            self.importFinished.emit(str(new_path), f"Imported, but failed to save metadata:\n{exc}")
+            return
+
+        self._refresh_files(show_empty_message=False)
+        self.importFinished.emit(str(new_path), f"Imported {new_filename}")
+
     # ===== Internal Data Loading =====
     def _refresh_files(self, show_empty_message: bool) -> None:
         selected_state = {

src/pygui/backend/visualization/wafer_map_item.py

@@ -124,7 +124,7 @@ class WaferMapItem(QQuickPaintedItem):
         self._margin:   float = 1.0
         self._blend:    float = 0.0
         self._show_labels: bool = True
-        self._show_extremes: bool = False
+        self._show_extremes: bool = True
         self._shape: str = "round"
         self._size: float = 300.0
         self._thickness_data: list[list[float]] = []  # [x_mm, y_mm, t2] triples

src/pygui/backend/wafer/zwafer_parser.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from datetime import datetime
 from pathlib import Path
 from typing import Optional, Tuple
@@ -74,6 +76,31 @@ class ZWaferParser:
 
         return wafer_data  # Incomplete file — return partial data
 
+    # ===== Data Row Extraction =====
+    def parse_data_rows(self, file_path: str) -> list[str]:
+        """Return data rows after the 'data' marker, with the leading
+        row-index column stripped (each row realigned to `csv_headers`).
+
+        Uses the same line normalization as `_process_header` so the split
+        point matches exactly what header parsing used.
+        """
+        rows: list[str] = []
+        seen_data_marker = False
+        with Path(file_path).open("r", encoding="utf-8") as f:
+            for raw_line in f:
+                line = raw_line.rstrip().rstrip(",").strip()
+                if not line or line.replace(",", "").strip() == "":
+                    continue
+
+                parts = [p.strip() for p in line.split(",")]
+                if not seen_data_marker:
+                    if parts[0].lower() == "data":
+                        seen_data_marker = True
+                    continue
+
+                rows.append(",".join(parts[1:]))
+        return rows
+
     # ===== Metadata Parsing =====
     def _parse_header_line(self, wafer_data: ZWaferData, parts: list) -> bool:
         """Parse key=value pairs from header line. Returns True if handled."""