feat: xorg text overlays, font atlas generator, v4l2_view_cli

- tools/gen_font_atlas: Python/Pillow build tool — skyline packs DejaVu
  Sans glyphs 32-255 into a grayscale atlas, emits build/gen/font_atlas.h
  with pixel data and Font_Glyph[256] metrics table
- xorg: bitmap font atlas text overlay rendering (GL_R8 atlas texture,
  alpha-blended glyph quads, dark background rect per overlay)
- xorg: add xorg_viewer_set_overlay_text / clear_overlays API
- xorg: add xorg_viewer_handle_events for streaming use (events only,
  no redundant render)
- xorg_cli: show today's date as white text overlay
- v4l2_view_cli: new tool — V4L2 capture with format auto-selection
  (highest FPS then largest resolution), MJPEG/YUYV, measured FPS overlay
- docs: update README, planning, architecture to reflect current status

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

dev/cli/Makefile

@@ -22,7 +22,8 @@ CLI_SRCS = \
 	protocol_cli.c \
 	query_cli.c \
 	test_image_cli.c \
-	xorg_cli.c
+	xorg_cli.c \
+	v4l2_view_cli.c
 
 CLI_OBJS = $(CLI_SRCS:%.c=$(CLI_BUILD)/%.o)
 
@@ -37,7 +38,8 @@ all: \
 	$(CLI_BUILD)/protocol_cli \
 	$(CLI_BUILD)/query_cli \
 	$(CLI_BUILD)/test_image_cli \
-	$(CLI_BUILD)/xorg_cli
+	$(CLI_BUILD)/xorg_cli \
+	$(CLI_BUILD)/v4l2_view_cli
 
 # Module objects delegate to their sub-makes.
 $(COMMON_OBJ):      ; $(MAKE) -C $(ROOT)/src/modules/common
@@ -83,6 +85,9 @@ $(CLI_BUILD)/test_image_cli: $(CLI_BUILD)/test_image_cli.o $(TEST_IMAGE_OBJ)
 $(CLI_BUILD)/xorg_cli: $(CLI_BUILD)/xorg_cli.o $(TEST_IMAGE_OBJ) $(XORG_OBJ)
 	$(CC) $(CFLAGS) -o $@ $^ $(PKG_LDFLAGS)
 
+$(CLI_BUILD)/v4l2_view_cli: $(CLI_BUILD)/v4l2_view_cli.o $(XORG_OBJ)
+	$(CC) $(CFLAGS) -o $@ $^ $(PKG_LDFLAGS)
+
 $(CLI_BUILD):
 	mkdir -p $@
 
@@ -98,6 +103,7 @@ clean:
 		$(CLI_BUILD)/protocol_cli \
 		$(CLI_BUILD)/query_cli \
 		$(CLI_BUILD)/test_image_cli \
-		$(CLI_BUILD)/xorg_cli
+		$(CLI_BUILD)/xorg_cli \
+		$(CLI_BUILD)/v4l2_view_cli
 
 -include $(CLI_OBJS:%.o=%.d)