legal: bundle third-party licenses on the ISO; stop shipping doom1.wad

- New 0:/os/licenses/ directory on the ISO with GPL-3.0.txt (Flat Remix
  icon theme), GPL-2.0.txt (doomgeneric DOOM engine), and NOTICES.txt
  (mirrors montaukos.org/THIRD-PARTY-NOTICES.txt).
- THIRD-PARTY-NOTICES.txt gains a Flat Remix section (GPLv3, attribution,
  modification and corresponding-source statements; the shipped SVGs are
  the source form).
- man legal now lists third-party components and points at 0:/os/licenses/.
- doom1.wad removed from the repo and the build: the shareware WAD is
  proprietary id Software content. doom.elf (GPLv2) still ships; users
  must supply their own WAD.

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

scripts/install_apps.sh

@@ -80,9 +80,7 @@ done
 
 rm -rf "$BIN/apps/dialogs"
 
-# Special case: copy doom1.wad alongside doom binary
-if [ -f "$PROJECT_ROOT/programs/data/games/doom1.wad" ]; then
-    cp "$PROJECT_ROOT/programs/data/games/doom1.wad" "$BIN/apps/doom/doom1.wad"
-fi
+# DOOM game data (doom1.wad) is proprietary id Software content and is
+# deliberately NOT bundled; the engine (doom.elf, GPLv2) ships without it.
 
 echo "install_apps: installed $installed app bundles to $BIN/apps/"