Add Chinese text rendering support

Extend the bitmap font pipeline with the Chinese Joker glyph subset and encode supported UTF-8 text for Tonc TTE. Move the affine map clear of the expanded font, add a compile-time VRAM overlap guard, and cover every custom glyph with host tests.

tests/chinese_text/Makefile

@@ -0,0 +1,15 @@
+CC := gcc
+CFLAGS := -I../../include -I. \
+          -g -O3 -std=gnu23 -Wall -Werror
+SRC            := chinese_text_test.c       \
+                  ../../source/chinese_text.c
+OUT            := build/chinese_text_test
+
+$(OUT): $(SRC) | build
+	$(CC) $(CFLAGS) -o $@ $^
+
+build:
+	mkdir -p build
+
+clean:
+	rm -f $(OUT)