BC-250 console image: custom GNOME recipe with remote admin

Based on 62fixolab/Latest-Bazzite-AMD-BC-250-Patched-Images @ 347fd4d.

Adds on top of the fork:
- recipes/bc250-console-gnome.yml: governor + gnome-remote-desktop +
  openssh-server, sshd enabled, hhd.service masked, no signing module
  (local build + ISO path)
- files/console/usr/bin/bc250-remote-setup: one-time on-box SSH/RDP setup
- files/console/usr/lib/bootc/kargs.d/50-bc250-ttm.toml: ttm memory kargs
- BUILD-CONSOLE.md: build -> ISO -> validation instructions

files/console/ is separate from files/system/ so the 40-CU unlock tooling
stays out of this stable 24-CU image.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/render-channel-recipe.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env python3
+"""Render a BlueBuild recipe for a specific Bazzite channel and package name."""
+
+from __future__ import annotations
+
+import argparse
+from pathlib import Path
+
+
+def replace_prefixed_line(lines: list[str], prefix: str, replacement: str) -> list[str]:
+    replaced = False
+    rendered: list[str] = []
+
+    for line in lines:
+        if line.startswith(prefix):
+            rendered.append(replacement)
+            replaced = True
+        else:
+            rendered.append(line)
+
+    if not replaced:
+        raise SystemExit(f"Could not find required line starting with {prefix!r}.")
+
+    return rendered
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--recipe", required=True, type=Path)
+    parser.add_argument("--output", required=True, type=Path)
+    parser.add_argument("--channel", required=True)
+    parser.add_argument("--name", required=True)
+    return parser.parse_args()
+
+
+def main() -> int:
+    args = parse_args()
+
+    lines = args.recipe.read_text(encoding="utf-8").splitlines()
+    lines = replace_prefixed_line(lines, "name:", f"name: {args.name}")
+    lines = replace_prefixed_line(lines, "image-version:", f"image-version: {args.channel}")
+    lines = [
+        line.replace(" stable image ", f" {args.channel} image ")
+        if line.startswith("description:")
+        else line
+        for line in lines
+    ]
+
+    args.output.write_text("\n".join(lines) + "\n", encoding="utf-8")
+    print(f"Rendered {args.output} for {args.name}:{args.channel}")
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())