test: add sim-yellow and sim-red envs for visual border verification

Two pio envs that build a tiny sketch reading /img.bin from LittleFS and
calling epd_draw_image_with_border with the chosen color. Lets us verify
the actual on-device pixel composition of the sync-fail (yellow) and
no-WiFi (red) borders without standing up a server failure or pulling
the WiFi cable.

Each sim sets NVS err_border=1 before halting, so flashing back to the
normal env afterwards exercises the 304 → clean repaint recovery path
end-to-end.

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

platformio.ini

@@ -31,3 +31,36 @@ lib_deps =
     throwtheswitch/Unity@^2.6
 build_flags = -DUNIT_TEST -std=c++17 -iquote test/mocks -iquote test -Itest/mocks -Itest
 test_build_src = no
+
+; Visual hardware tests for the sync-fail / no-WiFi border. Reads the cached
+; /img.bin from LittleFS and draws it with a yellow / red border. Sets
+; NVS err_border=1 so the next normal-firmware boot exercises the recovery
+; redraw via 304. Flow:
+;   1. pio run -e sim-yellow --target upload  (see yellow border on hardware)
+;   2. pio run -e sim-red    --target upload  (see red border on hardware)
+;   3. pio run -e esp32dev   --target upload  (back to normal; verifies 304 recovery)
+[env:sim-yellow]
+platform = espressif32
+board = esp32dev
+framework = arduino
+monitor_speed = 115200
+upload_port = /dev/ttyUSB0
+monitor_port = /dev/ttyUSB0
+board_build.filesystem = littlefs
+build_flags = -DSIM_BORDER -DSIM_BORDER_COLOR=COLOR_YELLOW
+build_src_filter = +<epd.cpp> +<sim_border.cpp>
+lib_deps =
+    ricmoo/QRCode@^0.0.1
+
+[env:sim-red]
+platform = espressif32
+board = esp32dev
+framework = arduino
+monitor_speed = 115200
+upload_port = /dev/ttyUSB0
+monitor_port = /dev/ttyUSB0
+board_build.filesystem = littlefs
+build_flags = -DSIM_BORDER -DSIM_BORDER_COLOR=COLOR_RED
+build_src_filter = +<epd.cpp> +<sim_border.cpp>
+lib_deps =
+    ricmoo/QRCode@^0.0.1