add MCP developer tool with multi-unit support

First developer tool for the XDJ-100SX project. Connects Claude Code
directly to the Pi over SSH — push skin files, take screenshots, restart
Mixxx, flash Pico firmware, and more without leaving the editor.

Available MCP tools:
- run_command, read_file, write_file, list_files
- push_skin, pull_skin, push_skin_file, pull_skin_file
- push_midi, pull_midi
- take_screenshot, navigate_panel
- restart_mixxx
- check (preflight: SSH, Mixxx, Pico, audio)
- pico_bootloader, pico_flash
- discover_units — scan network for all reachable XDJ Pi units
- select_unit — switch active connection mid-session (multi-unit support)

Also adds --about flag and TUI About modal with authors and credits,
and fixes scrolling/close behavior on Help and About modals.

By: Jeancarlo Cardoso de Faria Filho (jaianlab) <jaianlabworks@gmail.com>

tools/xdj_pi_dev/image_utils.py

@@ -0,0 +1,127 @@
+from __future__ import annotations
+
+"""
+Image utilities: white-background removal and PIL-image → Rich-Text rendering.
+
+Half-block trick: the ▄ character covers the BOTTOM half of a terminal cell.
+  • Both halves opaque  → bgcolor=top, color=bottom, char=▄
+  • Top transparent     → color=bottom, no bgcolor (panel bg shows through), char=▄
+  • Bottom transparent  → color=top, no bgcolor, char=▀  (upper-half block)
+  • Both transparent    → space (panel background shows through)
+
+This avoids any fixed background-colour guessing, so the image blends naturally
+against whatever Textual's panel colour happens to be.
+"""
+
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from PIL import Image as _PILImage
+
+_IMAGES_DIR = Path(__file__).parent / "images"
+
+# Pixels with alpha below this are treated as fully transparent
+_ALPHA_THRESH = 80
+
+
+def _remove_white_bg(img: "_PILImage.Image", threshold: int = 230) -> "_PILImage.Image":
+    """
+    BFS flood-fill from all four corners: connected white pixels become transparent.
+    Corner-flood avoids touching white silkscreen text on the board itself.
+    """
+    img = img.convert("RGBA")
+    w, h = img.size
+    pixels = img.load()
+
+    def _is_white(px) -> bool:
+        return px[0] >= threshold and px[1] >= threshold and px[2] >= threshold
+
+    visited: set[tuple[int, int]] = set()
+    queue: list[tuple[int, int]] = []
+    for sx, sy in [(0, 0), (w - 1, 0), (0, h - 1), (w - 1, h - 1)]:
+        if _is_white(pixels[sx, sy]) and (sx, sy) not in visited:
+            queue.append((sx, sy))
+            visited.add((sx, sy))
+
+    while queue:
+        x, y = queue.pop()
+        r, g, b, _ = pixels[x, y]
+        pixels[x, y] = (r, g, b, 0)
+        for nx, ny in ((x - 1, y), (x + 1, y), (x, y - 1), (x, y + 1)):
+            if 0 <= nx < w and 0 <= ny < h and (nx, ny) not in visited:
+                if _is_white(pixels[nx, ny]):
+                    visited.add((nx, ny))
+                    queue.append((nx, ny))
+
+    return img
+
+
+def img_to_rich(img: "_PILImage.Image", target_width: int = 32) -> object:
+    """
+    Convert a PIL RGBA image to a Rich Text object using half-block characters.
+    Transparent areas render as plain spaces so the panel background shows through.
+    Returns a rich.text.Text ready to pass to Static() or RichLog.write().
+    """
+    from PIL import Image
+    from rich.text import Text
+    from rich.style import Style
+    from rich.color import Color
+
+    aspect = img.height / img.width
+    target_height = max(2, int(target_width * aspect * 0.5) * 2)  # must be even
+    img = img.resize((target_width, target_height), Image.LANCZOS).convert("RGBA")
+    pixels = img.load()
+
+    result = Text(no_wrap=True)
+    for row in range(0, target_height, 2):
+        if row > 0:
+            result.append("\n")
+        for col in range(target_width):
+            tr, tg, tb, ta = pixels[col, row]
+            br, bg, bb, ba  = pixels[col, min(row + 1, target_height - 1)]
+            top_opaque = ta > _ALPHA_THRESH
+            bot_opaque = ba > _ALPHA_THRESH
+
+            if not top_opaque and not bot_opaque:
+                # Both transparent — let the panel background show through
+                result.append(" ")
+            elif top_opaque and bot_opaque:
+                # Both opaque — full half-block encoding
+                result.append("▄", style=Style(
+                    bgcolor=Color.from_rgb(tr, tg, tb),
+                    color=Color.from_rgb(br, bg, bb),
+                ))
+            elif not top_opaque and bot_opaque:
+                # Bottom opaque, top transparent — ▄ with no background
+                result.append("▄", style=Style(color=Color.from_rgb(br, bg, bb)))
+            else:
+                # Top opaque, bottom transparent — upper-half block, no background
+                result.append("▀", style=Style(color=Color.from_rgb(tr, tg, tb)))
+    return result
+
+
+def load_board_rich(board_key: str, target_width: int = 32) -> object | None:
+    """
+    Load, background-remove, and render a board image as Rich Text.
+    Returns None if Pillow is not installed or the image is missing.
+    board_key: 'pico' | 'pico2' | 'teensy'
+    """
+    _FILE_MAP = {
+        "pico":   "raspberry pi pico.png",
+        "pico2":  "raspberry pi pico 2.png",
+        "teensy": "teensy 4-0.png",
+    }
+    fname = _FILE_MAP.get(board_key)
+    if not fname:
+        return None
+    path = _IMAGES_DIR / fname
+    if not path.exists():
+        return None
+    try:
+        from PIL import Image
+        img = Image.open(path)
+        img = _remove_white_bg(img)
+        return img_to_rich(img, target_width)
+    except Exception:
+        return None