Restructure: ship only the component; move dev-only trees out

components/gxepd2/ now contains only what the device build compiles. The
vendored GxEPD2 source (3MB, host-capture only) moves to third_party/GxEPD2/,
its build shim to third_party/arduino_compat/, and the reference catalog to
tools/gxepd2_catalog/catalog.json beside its generator. None of these were in
the device include graph; they were only shipped as dead weight via
external_components. Also drops the obsolete busy_pin_polarity.md (that fact
now lives in each descriptor's busy_active_level, read automatically by the
capture probe). Comment path references and the catalog generator's paths
updated; device build, harness emit, and catalog regen all verified.

components/gxepd2/busy_pin_polarity.md

@@ -1,23 +0,0 @@
-# Busy pin polarity, by panel
-
-Started as "capture it when we happen upon it, not full project scope" on
-the assumption we'd need each controller's datasheet to explain *why* a
-panel is active-high/low on BUSY. Turns out GxEPD2 already has this as
-data, not something to derive: every vendor driver's constructor passes
-its own `busy_level` literal to `GxEPD2_EPD(cs, dc, rst, busy, busy_level,
-...)`, which is exactly what `EpdPanelDescriptor::busy_active_level`
-encodes per-panel here. So this **is** in scope to track for every panel,
-not just ones we happen to touch - just not yet: pinned as a later task to
-go read it off every vendor driver in one pass, rather than accreting it
-incidentally the way this table has so far.
-
-| Panel | Controller | busy_level (vendor ctor) | busy_active_level | Hardware-confirmed? |
-|---|---|---|---|---|
-| GDEY0213Z98 | SSD1680 | HIGH | true | yes (bench panel, working) |
-| GDEQ0426T82 | SSD1677 | HIGH | true | yes (2026-09-19) |
-| GDEQ0583T31 | UC8179 | LOW | false | pending |
-| GDEY029F51 | JD79667 | LOW | false | no (4-color, not yet ported to this engine) |
-| GDEY0579F51 | HX8717 | LOW | false | no (4-color, not yet ported to this engine) |
-
-Source: each driver's own `.cpp`, `GxEPD2_EPD(cs, dc, rst, busy, <level>, ...)`
-constructor call (grep `GxEPD2_EPD(cs, dc, rst, busy` in `vendor/src/**/*.cpp`).

components/gxepd2/cycle_engine.h

@@ -180,7 +180,7 @@ class CycleEngine {
   // Every command byte and every data byte is its own SPI transaction, CS
   // toggled around each one - this looks wasteful, but it's mechanically
   // what GxEPD2_EPD::_writeCommand()/_writeData(uint8_t) do (see
-  // vendor/src/GxEPD2_EPD.cpp), and matching the vendor cycle byte-for-byte
+  // third_party/GxEPD2/src/GxEPD2_EPD.cpp), and matching the vendor cycle byte-for-byte
   // is the point of this engine.
   void write_byte_(uint8_t b, bool dc_high) {
     this->dc_->digital_write(dc_high);

components/gxepd2/panel_213_z98c.h

@@ -1,7 +1,7 @@
 #pragma once
 
 // GDEY0213Z98, SSD1680 controller, 128x250 RAM window (122 columns visible),
-// black + red. Derived from vendor/src/epd3c/GxEPD2_213_Z98c.{h,cpp}.
+// black + red. Derived from third_party/GxEPD2/src/epd3c/GxEPD2_213_Z98c.{h,cpp}.
 
 #include "epd_command.h"
 

components/gxepd2/panel_213c_gdey0213f51.h

@@ -1,6 +1,6 @@
 #pragma once
 
-// Hand-derived from vendor/src/epd4c/GxEPD2_213c_GDEY0213F51.{h,cpp}
+// Hand-derived from third_party/GxEPD2/src/epd4c/GxEPD2_213c_GDEY0213F51.{h,cpp}
 // (GDEY0213F51, JD79661 controller, 128x250 buffer / 122x250 visible,
 // 4-color BWRY). Same Good Display 4-color command template as
 // panel_290c_gdey029f51.h (JD79667) - the _InitDisplay() command sequence is

components/gxepd2/panel_213c_gdey0213f52.h

@@ -5,7 +5,7 @@
 // bench F52 panels actually are (see the F51-vs-F52 control-diff memory).
 //
 // Emitter-derived (tools/gxepd2_harness/emit_descriptor.h) from the vendor
-// GxEPD2_213c_GDEY0213F52 driver pulled into vendor/ from the zGxEPD2 fork.
+// GxEPD2_213c_GDEY0213F52 driver pulled into third_party/GxEPD2/ from the zGxEPD2 fork.
 // The striking thing the capture shows: this driver is *minimal* because the
 // JD79676 loads PSR/PWR/BTST/resolution and the full-refresh LUT from on-chip
 // OTP. So init is just 0xE9=0x01 then power-on (0x04), there is NO register

components/gxepd2/panel_290c_gdey029f51.h

@@ -1,6 +1,6 @@
 #pragma once
 
-// Hand-derived from vendor/src/epd4c/GxEPD2_290c_GDEY029F51.{h,cpp}
+// Hand-derived from third_party/GxEPD2/src/epd4c/GxEPD2_290c_GDEY029F51.{h,cpp}
 // (GDEY029F51, JD79667 controller, 128x296, 4-color BWRY panel used here as
 // black/white/red via the black+color buffer interface). First panel on a
 // completely different command set from the SSD1680/1677/UC8179 mono

components/gxepd2/panel_426_gdeq0426t82.h

@@ -1,6 +1,6 @@
 #pragma once
 
-// Hand-derived from vendor/src/gdeq/GxEPD2_426_GDEQ0426T82.{h,cpp}
+// Hand-derived from third_party/GxEPD2/src/gdeq/GxEPD2_426_GDEQ0426T82.{h,cpp}
 // (GDEQ0426T82, SSD1677 controller, 800x480, monochrome). First panel with
 // a genuine current/previous differential RAM (0x24/0x26) - the vendor
 // driver's writeImageAgain()/writeImageForFullRefresh() keep both buffers

components/gxepd2/panel_579c_gdey0579f51.h

@@ -1,6 +1,6 @@
 #pragma once
 
-// Hand-derived from vendor/src/epd4c/GxEPD2_579c_GDEY0579F51.{h,cpp}
+// Hand-derived from third_party/GxEPD2/src/epd4c/GxEPD2_579c_GDEY0579F51.{h,cpp}
 // (GDEY0579F51, HX8717 controller, 792x272, same JD79667-family 2bpp/4-color
 // packing as GDEY029F51 - see panel_290c_gdey029f51.h). The real dual-
 // region version, superseding panel_579c_gdey0579f51_master_only.h's

components/gxepd2/panel_579c_gdey0579f51_master_only.h

@@ -1,6 +1,6 @@
 #pragma once
 
-// Hand-derived from vendor/src/epd4c/GxEPD2_579c_GDEY0579F51.{h,cpp}
+// Hand-derived from third_party/GxEPD2/src/epd4c/GxEPD2_579c_GDEY0579F51.{h,cpp}
 // (GDEY0579F51, HX8717 controller, 792x272, same JD79667-family 2bpp/4-color
 // packing as GDEY029F51 - see panel_290c_gdey029f51.h). This is the actual
 // dual-CS-like split panel from the original bench list: NOT two physical

components/gxepd2/panel_583_gdeq0583t31.h

@@ -1,6 +1,6 @@
 #pragma once
 
-// Hand-derived from vendor/src/gdeq/GxEPD2_583_GDEQ0583T31.{h,cpp}
+// Hand-derived from third_party/GxEPD2/src/gdeq/GxEPD2_583_GDEQ0583T31.{h,cpp}
 // (GDEQ0583T31, UC8179 controller, 648x480, monochrome).
 //
 // Structurally the oddest of the panels covered so far: UC8179 has no