feat(13e6): bring up Waveshare 13.3" Spectra-6 end-to-end

Adds a second panel target alongside the 7.3":
- src/panels/waveshare13e6/v1/ — full epd.h impl with hardware SPI on
  FSPI, dual-CS dispatch (CS_M/CS_S split halves), PSRAM framebuffer
  for image/QR/setup-screen render paths
- src/test_display_13e6.cpp + [env:test-display-13e6] — self-contained
  first-pixels color-bar smoke test, kept as a hardware diagnostic
- [env:waveshare13e6-v1] — production env: ESP32-S3-WROOM-2 N32R16V
  with OPI flash + OPI PSRAM (the WROOM-2 is octal flash; QIO mode
  crashes at do_core_init startup.c:328)
- scripts/gen_screens_13e6.py + data/waveshare13e6-v1/ — 1200x1600
  portrait setup screens with QR overlay regions matching the driver
- scripts/data_dir.py — extra_scripts shim that routes uploadfs to the
  right data/ tree based on $PIOENV (PlatformIO ignores per-env data_dir)
- src/epd.h: epd_setup_pins() abstraction so each panel driver owns its
  own pinMode + SPI.begin; main/test_display/sim_border lose all
  panel-specific GPIO and call epd_setup_pins() once at boot
- src/operation.h: report PANEL_ID via X-Panel-Id header on every poll
  so the server can auto-correct Device.model

7.3" production env stays byte-identical, all 43 native tests pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

test/mocks/epd_mock.h

@@ -16,6 +16,7 @@ extern int g_epd_draw_border_count;
 extern int g_epd_draw_border_last_color;
 extern int g_epd_draw_border_last_thickness;
 
+inline void epd_setup_pins() {}
 inline void epd_init()  { g_epd_init_count++; }
 inline void epd_sleep() { g_epd_sleep_count++; }
 inline void epd_draw_image_from_file(File& f) {