Terminal: Das prompt, dprompt and dbanner (0.9.1)

- das-shell 0.1.0: the Das two-line bash prompt by default (replaces the
  PS1 of Void's skel .bashrc once), dprompt (Textual prompt builder with
  presets and live preview) and dbanner (SSH login banner editor: canvas
  tools, fields with values, widgets, das-banner service for cached ones,
  Das OS logo and tryzub pictures). Python tests in make test.
- das-server 0.3.0 depends on das-shell; the server installer mentions
  dprompt and dbanner; the desktop image includes it.
- run-qemu.sh forwards the guest's SSH to localhost:2222.
- Hardware fixes: Ventoy menu icon, boot menu titles "Das OS <version>".

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/art2cells.py

@@ -0,0 +1,101 @@
+#!/usr/bin/env python3
+"""Turns an SVG into a dbanner picture: half-block cells (▀ ▄ █) in ANSI colors.
+
+    tools/art2cells.py SVG WIDTH_PX HEIGHT_PX NAME "UK title" "EN title" \
+        "#rrggbb=ansi_name" ... [--mirror] > srcpkgs/das-shell/files/share/banner/art/NAME.json
+
+Each output cell holds two square pixels, so HEIGHT_PX must be even. The SVG is
+drawn 8 times larger by ImageMagick, and every pixel takes the color that
+covers most of its 8x8 block (or stays empty). Colors are matched to the
+nearest one given on the command line; --mirror copies the left half to the
+right for symmetric pictures. Needs ImageMagick and Pillow; this is a
+developer tool, the package ships only the JSON.
+"""
+
+import json
+import os
+import subprocess
+import sys
+import tempfile
+from collections import Counter
+
+from PIL import Image
+
+SCALE = 8
+
+
+def main():
+    args = sys.argv[1:]
+    mirror = "--mirror" in args
+    if mirror:
+        args.remove("--mirror")
+    svg, width, height, name, uk, en, *pairs = args
+    width, height = int(width), int(height)
+    palette = []
+    for pair in pairs:
+        hexcolor, ansi = pair.split("=")
+        palette.append((tuple(int(hexcolor[i:i + 2], 16) for i in (1, 3, 5)), ansi))
+
+    with tempfile.TemporaryDirectory() as tmp:
+        png = os.path.join(tmp, "art.png")
+        subprocess.run(["convert", "-background", "none", "-density", "600", svg,
+                        "-resize", f"{width * SCALE}x{height * SCALE}!", png], check=True)
+        img = Image.open(png).convert("RGBA")
+
+    def nearest(rgb):
+        return min(palette, key=lambda p: sum((a - b) ** 2 for a, b in zip(p[0], rgb)))[1]
+
+    pixels = []
+    for py in range(height):
+        row = []
+        for px in range(width):
+            votes = Counter()
+            for y in range(py * SCALE, (py + 1) * SCALE):
+                for x in range(px * SCALE, (px + 1) * SCALE):
+                    r, g, b, a = img.getpixel((x, y))
+                    votes[nearest((r, g, b)) if a >= 128 else None] += 1
+            row.append(votes.most_common(1)[0][0])
+        if mirror:
+            # The source is symmetric; rounding is not, so copy the left half
+            for x in range(width // 2):
+                row[width - 1 - x] = row[x]
+        pixels.append(row)
+
+    styles, keys = {}, "abcdefghijklmnopqrstuvwxyz"
+
+    def key(fg, bg):
+        want = {"fg": fg, "bg": bg, "bold": False}
+        for k, v in styles.items():
+            if v == want:
+                return k
+        k = keys[len(styles)]
+        styles[k] = want
+        return k
+
+    lines, smap = [], []
+    for cy in range(height // 2):
+        line, keyline = "", ""
+        for x in range(width):
+            top, bottom = pixels[2 * cy][x], pixels[2 * cy + 1][x]
+            if top is None and bottom is None:
+                ch, k = " ", " "
+            elif top == bottom:
+                ch, k = "█", key(top, None)
+            elif bottom is None:
+                ch, k = "▀", key(top, None)
+            elif top is None:
+                ch, k = "▄", key(bottom, None)
+            else:
+                ch, k = "▀", key(top, bottom)
+            line += ch
+            keyline += k
+        lines.append(line.rstrip())
+        smap.append(keyline[:len(line.rstrip())])
+    design = {"name": name, "title": {"uk": uk, "en": en}, "styles": styles,
+              "lines": lines, "style_map": smap}
+    json.dump(design, sys.stdout, ensure_ascii=False, indent=2)
+    sys.stdout.write("\n")
+
+
+if __name__ == "__main__":
+    main()