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.

docs/preparing-your-mod-for-gen2.md

@@ -176,7 +176,7 @@ something the filesystem encodes.
 
 | token | means |
 | --- | --- |
-| `"red"`, `"blue"`, `"yellow"`, `"gold"` | that one game (a version id from `GameVersion.ORDER`) |
+| `"red"`, `"blue"`, `"yellow"`, `"gold"`, `"silver"` | that one game (a version id from `GameVersion.ORDER`) |
 | `"gen1"`, `"gen2"` | every game of that generation (case-insensitive; `"gen 2"` also parses) |
 | `"all"` | every game this engine has |