Pokemon Silver as a full launcher version, plus launcher mods-list and title-tempo fixes

Silver: derived import manifest (tools/make_silver_manifest.py re-resolves
the Gold manifest's symbols from pokesilver.sym), silver GameVersion row,
generation-keyed extractor routing, required-files override, edition save
stamping (a Silver playthrough no longer writes into the Gold save),
checkver-driven edition data, SILVER/KAMON/OSCAR/MAX presets, GOLD rival
default, edition credits banner, Lugia title screen (OAM layouts, bob,
trail, palettes as title.lua data keys with Gold defaults so old caches
need no re-import), packaging for every build target, docs, and tests.

Launcher: the installed-mods list is one continuous scroll (rows culled to
the viewport) instead of a pager with an inner scroll viewport; the pad
cursor's edge-scroll no longer runs it to the bottom. The game dropdown
shows just the initial and caret. Find-tab behavior unchanged.

Title tempo: a sprite-anim frame shows duration+1 ticks
(engine/sprite_anims/core.asm GetSpriteAnimFrame), which locks both
editions' 64-tick wing beat to the 64-tick sine bob; the title screens no
longer run fast and out of phase.

scripts/linux-arm64/build_appimage.sh

@@ -366,6 +366,8 @@ cp "$IN/game.love" "$APPDIR/game.love"
 unzip -Z1 "$APPDIR/game.love" > "$WORK/love-listing.txt"
 grep -qxF "tools/rom_manifest_gold.json" "$WORK/love-listing.txt" \
   || fail "game.love is missing tools/rom_manifest_gold.json"
+grep -qxF "tools/rom_manifest_silver.json" "$WORK/love-listing.txt" \
+  || fail "game.love is missing tools/rom_manifest_silver.json"
 # The .desktop's Icon= resolves against the AppDir root by basename, and
 # .DirIcon is what appimaged and file-manager thumbnailers read.
 cp "$IN/icon.png" "$APPDIR/$APP_NAME.png"