feat(steami_screen): migrate steami_screen from tutorial repo

Author: Charly-sketch

lib/steami_screen/manifest.py

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+metadata(
+    description="Library for controlling the STeaMi round display.",
+    version="0.0.1",
+)
+
+package("steami_screen")

lib/steami_screen/steami_screen/__init__.py

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+from steami_screen.colors import rgb_to_gray4, rgb_to_rgb8, rgb_to_rgb565
+from steami_screen.screen import (
+    BLACK,
+    BLUE,
+    DARK,
+    GRAY,
+    GREEN,
+    LIGHT,
+    RED,
+    WHITE,
+    YELLOW,
+    Screen,
+)
+
+__all__ = [
+    "BLACK",
+    "BLUE",
+    "DARK",
+    "GRAY",
+    "GREEN",
+    "LIGHT",
+    "RED",
+    "WHITE",
+    "YELLOW",
+    "Screen",
+    "rgb_to_gray4",
+    "rgb_to_rgb8",
+    "rgb_to_rgb565",
+]

lib/steami_screen/steami_screen/colors.py

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+"""
+Color conversion utilities for STeaMi display backends.
+
+Colors are represented as RGB tuples (r, g, b) with values 0-255.
+Each backend converts to its native format:
+  - SSD1327 : grayscale 4-bit (0-15)
+  - GC9A01  : RGB565 (16-bit)
+  - Simulator: RGB tuple (pass-through)
+
+All functions accept legacy int values for backward compatibility.
+"""
+
+
+def rgb_to_gray4(color):
+    """Convert an RGB tuple to a 4-bit grayscale value (0-15).
+
+    Uses BT.601 luminance: Y = 0.299*R + 0.587*G + 0.114*B
+    Accepts int for backward compatibility (returned as-is, clamped to 0-15).
+    """
+    if isinstance(color, int):
+        return max(0, min(15, color))
+    r, g, b = color
+    luminance = (r * 77 + g * 150 + b * 29) >> 8  # 0-255
+    return luminance >> 4  # 0-15
+
+
+def rgb_to_rgb565(color):
+    """Convert an RGB tuple to a 16-bit RGB565 integer.
+
+    Accepts int for backward compatibility (treated as gray4, expanded).
+    """
+    if isinstance(color, int):
+        g = max(0, min(15, color)) * 17  # 0-255
+        r, b = g, g
+    else:
+        r, g, b = color
+    return ((r & 0xF8) << 8) | ((g & 0xFC) << 3) | (b >> 3)
+
+
+def rgb_to_rgb8(color):
+    """Convert a color to an RGB tuple (r, g, b).
+
+    If already a tuple, returns it unchanged.
+    Accepts int for backward compatibility (treated as gray4, expanded).
+    """
+    if isinstance(color, int):
+        v = max(0, min(15, color)) * 17  # 0-255
+        return (v, v, v)
+    return color