render: Game Boy chrome, LCD palette recolor, and frame capture

- --chrome: draw a DMG-style 'sl0pboy' shell around the LCD in sixel mode,
  with a bitmap-font silk-screen (logo, labels), speaker grille, power LED,
  and buttons that light up while held.
- LCD palette recolor (render_set_palette): remap the LCD to a 4-shade
  palette by luminance for the classic monochrome look ('dmg'/'green' pea
  green, 'pocket'/'gray'); applies to every render path.
- Refactor the sixel encoder into generic build_palette_buf/encode_sixel_buf
  operating on any RGB888 buffer, shared by the bare LCD and the chrome canvas.
- render_capture_size/frame: produce the exact displayed frame (recolor +
  chrome) as an RGB buffer, for screenshots and video recording.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/render.h b/src/render.h
index 03d6c7c..1be1290 100644
--- a/src/render.h
+++ b/src/render.h
@@ -11,6 +11,22 @@ void render_set_hud(int frameskip, bool turbo);  // update HUD readout
 // Switch terminal output to sixel graphics (scale = integer pixel zoom, >=1).
 // Pass on=false to use the default Unicode half-block renderer.
 void render_set_sixel(bool on, int scale);
+// Draw a Game Boy body/frame around the LCD (sixel output only); buttons on the
+// drawn shell light up while pressed. No effect unless sixel mode is enabled.
+void render_set_chrome(bool on);
+// Recolor the LCD output to a 4-shade palette by luminance, for the classic
+// monochrome-LCD look. Names: "dmg"/"green" (DMG-01 pea green), "pocket"/"gray"
+// (grayscale). NULL or unknown name = passthrough (true colors). Applies to
+// every render path (half-block, sixel, chrome).
+void render_set_palette(const char *name);
+
+// Frame capture for screenshots / video recording: produces the same pixels the
+// user sees, applying the LCD recolor palette and the Game Boy chrome when they
+// are enabled. render_capture_size reports the resulting dimensions (they only
+// change when chrome is toggled); render_capture_frame returns a pointer to an
+// internal contiguous RGB888 buffer (w*h*3 bytes, caller must not free).
+void render_capture_size(int *w, int *h);
+const u8 *render_capture_frame(GB *gb, int *w, int *h);
 // Poll keyboard + control FIFO, update gb->buttons. False if quit requested.
 bool input_poll(GB *gb);