Fix OLED display: remove bogus OLED_IC/FLIP_SEGMENT/128X64 defines and restore original rotation logic

The previous PR #5 added OLED defines (OLED_IC_SSD1312, OLED_DISPLAY_128X64,
OLED_FLIP_SEGMENT, etc.) from a hallucinated "Keebart vial_oled reference"
keymap that doesn't exist. These caused the display to be flipped horizontally
and upside down.

Restores:
- Original oled_init_user: default rotation for master, OLED_ROTATION_180 for slave
- is_keyboard_master() routing in oled_task_user
- Clean config.h without bogus OLED hardware defines
- Clean rules.mk without redundant OLED_DRIVER/OLED_TRANSPORT

Agent-Logs-Url: https://github.com/timfee/qmk_userspace/sessions/efa72aeb-690c-4f81-8e57-678197ccc4ab

Co-authored-by: timfee <3246342+timfee@users.noreply.github.com>

users/timfee/config.h

@@ -15,17 +15,7 @@
 #define COMBO_TERM 40
 #define COMBO_ONLY_FROM_LAYER 0
 
-// ── OLED (matches Keebart vial_oled reference) ──
-#define OLED_IC OLED_IC_SSD1312
-#define OLED_DISPLAY_128X64
-#define OLED_FLIP_SEGMENT
-#define OLED_DISPLAY_ADDRESS 0x3C
-#define OLED_CHARGE_PUMP_VALUE 0x72
-#define OLED_BRIGHTNESS 64
-#define OLED_TIMEOUT 0
-#define OLED_FADE_OUT
-
-// ── Split sync ──
+// ── OLED / split sync ──
 #define SPLIT_OLED_ENABLE
 #define SPLIT_WPM_ENABLE
 #define SPLIT_LAYER_STATE_ENABLE

users/timfee/rules.mk

@@ -1,5 +1,3 @@
 COMBO_ENABLE = yes
 WPM_ENABLE = yes
 OLED_ENABLE = yes
-OLED_DRIVER = ssd1306
-OLED_TRANSPORT = i2c

users/timfee/timfee.c

@@ -127,11 +127,14 @@ uint16_t get_quick_tap_term(uint16_t keycode, keyrecord_t *record) {
     }
 }
 
-// ── OLED display (rotation matches Keebart vial_oled reference) ──
+// ── OLED display ──
 #ifdef OLED_ENABLE
 
 oled_rotation_t oled_init_user(oled_rotation_t rotation) {
-    return OLED_ROTATION_90;
+    if (!is_keyboard_master()) {
+        return OLED_ROTATION_180;
+    }
+    return rotation;
 }
 
 static void render_layer(void) {
@@ -177,7 +180,7 @@ static void render_wpm(void) {
 }
 
 bool oled_task_user(void) {
-    if (is_keyboard_left()) {
+    if (is_keyboard_master()) {
         render_layer();
         render_keycode();
         render_wpm();