feat(map): add edge-center delta stats, thickness overlay, and layout fix

- Add edge-center sensor pair tables and delta calculations per wafer family.
- Parse and interpolate wafer thickness CSV data for offscreen visualization.
- Refactor ReadoutPanel layout using Item + anchors to fix right-margin clipping.
- Compact E-C Delta text format to fit standard sidebar width.
- Add pytest suite covering delta calculations, layout pairs, and thickness CSV.

src/pygui/backend/wafer/wafer_layouts.py

@@ -70,12 +70,35 @@ def _load_yaml(path: Path) -> dict:
         return loaded
 
 
-# TODO P6.3: expose this list to a new LayoutSelector.qml (4-button chooser)
-#   THINKING: this already returns everything the UI needs (family names) —
-#   the missing piece is a context-property exposure (SessionController or a
-#   thin new property) and a setLayout(family) slot that calls load_layout()
-#   below. No parsing work needed; this is a wiring-only task.
-#   See docs/pending/alpha-release-polish-plan.md §6.3.
+# Edge→center sensor pair tables, ported verbatim from the C# original
+# (Form1.cs ec_map_*). Indices are 0-origin. Domain data, not derivable from
+# ring geometry — see docs/adr/0002-edge-center-pair-tables.md.
+_EC_MAPS: dict[str, tuple[tuple[int, int], ...]] = {
+    "AEP": tuple((e, 40 + e // 2) for e in range(16)),
+    "BCD": tuple((e, 28) for e in range(12)),
+    "F": ((0, 18), (1, 19), (2, 19), (3, 19), (4, 20), (5, 20),
+          (6, 20), (7, 21), (8, 21), (9, 21), (10, 18), (11, 18)),
+    "X": ((5, 76), (0, 76), (39, 76), (6, 77), (11, 77), (16, 77),
+          (17, 78), (22, 78), (27, 78), (28, 79), (33, 79), (38, 79)),
+    "Z": tuple((e, 0) for e in range(49, 65)),
+}
+
+
+def ec_pairs_for_wafer_id(wafer_id: str) -> tuple[tuple[int, int], ...]:
+    """Edge-center pairs for a wafer id's family letter; empty if unknown.
+
+    Unknown families deliberately get no pairs (C# fell through to Z).
+    """
+    prefix = wafer_id[0].upper() if wafer_id else ""
+    for families, key in (("AEP", "AEP"), ("BCD", "BCD"), ("F", "F"),
+                          ("X", "X"), ("Z", "Z")):
+        if prefix and prefix in families:
+            return _EC_MAPS[key]
+    return ()
+
+
+# P6.3 (LayoutSelector) dropped 2026-07-10 — the C# "layout" buttons only
+# exported coordinate spreadsheets, decided obsolete. See MIGRATION.md.
 def available_families() -> list[str]:
     return [_family_name(_load_yaml(p)["name"]) for p in _LAYOUTS_DIR.glob("*.yaml")]