test pattern: label panels with dashed Good Display part number

The on-screen label is now the panel's Good Display part number in the
vendor's silkscreen form (GDEQ-0583T31, GDEY-0213Z98) instead of the GxEPD2
class trailer. Source of truth is the part number carried per model in
MODELS, because GxEPD2's older naming style drops the GDEx prefix and the
4-digit size - GxEPD2_213_Z98C is really GDEY0213Z98, which the class name
alone can't reconstruct (it labelled as "Z98C" before). A single regex
inserts the dash after the 4-char series prefix; size stays encoded once,
inside the part number.

components/gxepd2/display.py

@@ -7,6 +7,8 @@ extracted) EpdPanelDescriptor - see panel_213_z98c.h / panel_426_gdeq0426t82.h
 tree as reference material for panels not yet ported to this engine.
 """
 
+import re
+
 import esphome.codegen as cg
 import esphome.config_validation as cv
 from esphome import pins
@@ -48,21 +50,35 @@ CONF_NAME_FONT = "name_font"
 gxepd2_ns = cg.esphome_ns.namespace("gxepd2")
 GxEPD2Display = gxepd2_ns.class_("GxEPD2Display", display.DisplayBuffer)
 
-# model name -> C++ descriptor global (EpdPanelDescriptor) declared in the
-# matching panel_*.h header, which gxepd2_display.h includes unconditionally
-# - so any of these names can be selected without extra include wiring here.
+# model name -> (C++ descriptor global declared in the matching panel_*.h
+# header - gxepd2_display.h includes them all, so no extra include wiring here;
+# Good Display part number on the panel's silkscreen).
+#
+# The part number, not the GxEPD2 class name, is the source of truth for the
+# on-screen label (see _panel_label / test_pattern): GxEPD2's older naming
+# style drops the GDEx prefix and the 4-digit size - GxEPD2_213_Z98C is really
+# GDEY0213Z98 - so the class name alone can't reconstruct what's on the tag.
 MODELS = {
-    "GxEPD2_213_Z98C": "PANEL_213_Z98C",
-    "GxEPD2_426_GDEQ0426T82": "PANEL_426_GDEQ0426T82",
-    "GxEPD2_583_GDEQ0583T31": "PANEL_583_GDEQ0583T31",
-    "GxEPD2_290c_GDEY029F51": "PANEL_290C_GDEY029F51",
-    "GxEPD2_579c_GDEY0579F51": "PANEL_579C_GDEY0579F51",
+    "GxEPD2_213_Z98C": ("PANEL_213_Z98C", "GDEY0213Z98"),
+    "GxEPD2_426_GDEQ0426T82": ("PANEL_426_GDEQ0426T82", "GDEQ0426T82"),
+    "GxEPD2_583_GDEQ0583T31": ("PANEL_583_GDEQ0583T31", "GDEQ0583T31"),
+    "GxEPD2_290c_GDEY029F51": ("PANEL_290C_GDEY029F51", "GDEY029F51"),
+    "GxEPD2_579c_GDEY0579F51": ("PANEL_579C_GDEY0579F51", "GDEY0579F51"),
     # Debug variant: master half only, as if it were a self-contained
     # 396x272 panel - see panel_579c_gdey0579f51_master_only.h. Kept
-    # around as a diagnostic tool, not the panel's real mode.
-    "GxEPD2_579c_GDEY0579F51_MASTER_ONLY": "PANEL_579C_GDEY0579F51_MASTER_ONLY",
+    # around as a diagnostic tool, not the panel's real mode. Same physical
+    # part as the full panel, so same label.
+    "GxEPD2_579c_GDEY0579F51_MASTER_ONLY": ("PANEL_579C_GDEY0579F51_MASTER_ONLY", "GDEY0579F51"),
 }
 
+
+# Good Display part number -> shelf label: insert a dash after the 4-char GDEx
+# series prefix (GDEQ0583T31 -> GDEQ-0583T31), matching the vendor's own
+# silkscreen. The size stays encoded exactly once, inside the part number.
+# Anything not starting with GDE<letter> is returned untouched.
+def _panel_label(part: str) -> str:
+    return re.sub(r"^(GDE[A-Z])", r"\1-", part)
+
 CONFIG_SCHEMA = cv.All(
     display.FULL_DISPLAY_SCHEMA.extend(
         {
@@ -93,7 +109,8 @@ CONFIG_SCHEMA = cv.All(
 async def to_code(config: ConfigType) -> None:
     var = cg.new_Pvariable(config[CONF_ID])
 
-    cg.add(var.set_descriptor(cg.RawExpression(f"&esphome::gxepd2::{MODELS[config[CONF_MODEL]]}")))
+    descriptor, part_number = MODELS[config[CONF_MODEL]]
+    cg.add(var.set_descriptor(cg.RawExpression(f"&esphome::gxepd2::{descriptor}")))
     cg.add(var.set_cs_pin(await cg.gpio_pin_expression(config[CONF_CS_PIN])))
     cg.add(var.set_dc_pin(await cg.gpio_pin_expression(config[CONF_DC_PIN])))
     if reset_pin := config.get(CONF_RESET_PIN):
@@ -108,10 +125,10 @@ async def to_code(config: ConfigType) -> None:
     # will compute it from the (aliased) model. An explicit invert_mono wins.
     cg.add(var.set_invert_mono(config.get(CONF_INVERT_MONO, False)))
 
-    # Panel label for test_pattern(): the model trailer only (everything
-    # after the GxEPD2_<size> prefix, e.g. GxEPD2_583_GDEQ0583T31 ->
-    # GDEQ0583T31), so a tested panel shows what it is, not the C++ class id.
-    cg.add(var.set_model_name(config[CONF_MODEL].split("_", 2)[-1]))
+    # Panel label for test_pattern(): the Good Display part number in the
+    # vendor's dashed silkscreen form (GDEQ-0583T31), so a tested panel shows
+    # what it is on the shelf, not the GxEPD2 C++ class id.
+    cg.add(var.set_model_name(_panel_label(part_number)))
     if name_font := config.get(CONF_NAME_FONT):
         cg.add(var.set_name_font(await cg.get_variable(name_font)))