feat(q5_max): enable Keychron RGB and fix EEPROM persistence

Enable KEYCHRON_RGB_ENABLE for the Q5 Max, wiring up PER_KEY_RGB and
MIXED_RGB effects, and fix a cascade of EEPROM bugs that caused the
Launcher-configured RGB mode to revert to the default heatmap on every
power cycle and wireless transport change.

Keychron RGB enablement:
- Add KEYCHRON_RGB_ENABLE = yes to rules.mk
- Define default_per_key_led[] and default_region[] for the ANSI Encoder
  layout in ansi_encoder.c (extern'd by keychron_rgb.c)
- Fix missing #include "eeconfig_custom_rgb.h" in mixed_rgb.c and
  rgb_matrix_kb.inc so EECONFIG_SIZE_CUSTOM_RGB is in scope for the
  compile guards that gate the custom effects
- Add #undef EECONFIG_KB_DATA_SIZE before the Keychron redefinition in
  eeconfig_kb.h to suppress redefinition of QMK's default-zero value

EEPROM persistence fixes (keychron_rgb.c):
- Fix retail_demo_enable never being written to EEPROM in
  eeconfig_reset_custom_rgb(): original code used eeprom_read_block
  instead of eeprom_update_block, leaving 0xFF on freshly-flashed
  boards; retail_demo_task() treats any non-zero value as "demo active"
  and forces the mode to CUSTOM_MIXED_RGB every scan
- Clamp retail_demo_enable > 1 to 0 on load to recover boards already
  affected by the above bug
- Move EECONFIG_KEYBOARD version stamp from eeconfig_init_custom_rgb()
  (load path) to eeconfig_reset_custom_rgb() (reset/write path) so the
  version is only stamped when valid defaults are actually written
- Call eeconfig_update_rgb_matrix() in kc_rgb_save() so the current QMK
  RGB mode is persisted alongside Keychron data; without this,
  rgb_matrix_init() (called on every transport change) reloads the
  compile-time default RGB_MATRIX_TYPING_HEATMAP from EEPROM

Transport-change persistence (q5_max.c):
- Call eeconfig_init_custom_rgb() in keyboard_post_init_kb() so Keychron
  RGB arrays are loaded from EEPROM on every boot instead of being
  zero-initialised
- Add wireless_enter_connected_kb() hook: re-applies the EEPROM-saved
  QMK RGB mode after BT/2.4G reconnect in case the reconnect sequence
  resets the in-RAM mode before the display settles

DIP switch Win-side override (keymap.c):
- Replace rgb_matrix_mode() / rgb_matrix_sethsv() calls (which write to
  EEPROM and permanently overwrite the Launcher mode) with a
  dip_win_active flag; rgb_matrix_indicators_advanced_user() paints all
  LEDs white each frame when the flag is set, leaving the active effect
  and EEPROM untouched

VIA keymap address pinning (config.h):
- Define VIA_EEPROM_MAGIC_ADDR 544 to anchor VIA keymap storage at a
  fixed EEPROM offset; without this, growth in EECONFIG_KB_DATA_SIZE
  silently shifts the keymap block, corrupting stored layouts (observed
  as layer-0 keys reverting to KC_TRNS / KC_NONE on boot)

keyboards/keychron/common/rgb/keychron_rgb.c

@@ -76,7 +76,7 @@ void eeconfig_reset_custom_rgb(void) {
 
     eeprom_update_block(&os_ind_cfg, OFFSET_OS_INDICATOR, sizeof(os_ind_cfg));
     retail_demo_enable = 0;
-    eeprom_read_block(&retail_demo_enable, (uint8_t *)(OFFSET_RETAIL_DEMO), sizeof(retail_demo_enable));
+    eeprom_update_block(&retail_demo_enable, (uint8_t *)(OFFSET_RETAIL_DEMO), sizeof(retail_demo_enable));
     per_key_rgb_type = 0;
     eeprom_update_block(&per_key_rgb_type, OFFSET_PER_KEY_RGB_TYPE, sizeof(per_key_rgb_type));
 
@@ -100,15 +100,24 @@ void eeconfig_reset_custom_rgb(void) {
     effect_list[1][0].time = 5000;
 
     eeprom_update_block(effect_list, OFFSET_EFFECT_LIST, sizeof(effect_list));
+    eeprom_update_dword(EECONFIG_KEYBOARD, (EECONFIG_KB_DATA_VERSION));
     update_mixed_rgb_effect_count();
 }
 
 void eeconfig_init_custom_rgb(void) {
     memcpy(per_key_led, default_per_key_led, sizeof(per_key_led));
-    eeprom_update_dword(EECONFIG_KEYBOARD, (EECONFIG_KB_DATA_VERSION));
 
     eeprom_read_block(&os_ind_cfg, OFFSET_OS_INDICATOR, sizeof(os_ind_cfg));
     eeprom_read_block(&retail_demo_enable, (uint8_t *)(OFFSET_RETAIL_DEMO), sizeof(retail_demo_enable));
+    // Clamp to a valid boolean.  eeconfig_reset_custom_rgb() had a bug that
+    // used eeprom_read_block instead of eeprom_update_block for this byte,
+    // leaving EEPROM unwritten (often 0xFF on a freshly-flashed board).
+    // retail_demo_task() treats any non-zero value as "demo active" and forces
+    // the mode to CUSTOM_MIXED_RGB every scan, preventing mode changes.
+    if (retail_demo_enable > 1) {
+        retail_demo_enable = 0;
+        eeprom_update_block(&retail_demo_enable, (uint8_t *)(OFFSET_RETAIL_DEMO), sizeof(retail_demo_enable));
+    }
 
     if (os_ind_cfg.hsv.v < 128) os_ind_cfg.hsv.v = 128;
     // Load per key rgb led
@@ -283,6 +292,12 @@ static bool kc_rgb_save(void) {
     eeprom_update_block(regions, OFFSET_LAYER_FLAGS, RGB_MATRIX_LED_COUNT);
     eeprom_update_block(effect_list, OFFSET_EFFECT_LIST, sizeof(effect_list));
 
+    // Persist the current QMK RGB mode so it survives transport changes and
+    // power cycles.  Without this, rgb_matrix_init() reloads the EEPROM default
+    // (RGB_MATRIX_TYPING_HEATMAP) and the Launcher-configured mode is lost.
+    extern void eeconfig_update_rgb_matrix(void);
+    eeconfig_update_rgb_matrix();
+
     return true;
 }
 

keyboards/keychron/common/rgb/mixed_rgb.c

@@ -14,6 +14,10 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#ifdef KEYCHRON_RGB_ENABLE
+#    include "eeconfig_custom_rgb.h"
+#endif
+
 #if defined(KEYCHRON_RGB_ENABLE) && defined(EECONFIG_SIZE_CUSTOM_RGB)
 
 #include "quantum.h"

keyboards/keychron/common/rgb/rgb_matrix_kb.inc

@@ -15,6 +15,9 @@
  */
 
 #include "rgb_matrix_kb_config.h"
+#ifdef KEYCHRON_RGB_ENABLE
+#    include "eeconfig_custom_rgb.h"
+#endif
 
 #if defined(KEYCHRON_RGB_ENABLE) && defined(EECONFIG_SIZE_CUSTOM_RGB)
 //extern bool MIXED_RGB(effect_params_t *params);