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.

src/ui/gen2/Credits.lua

@@ -189,11 +189,18 @@ defineString("CREDIT_END", "END")
 
 -- STAFF and everything after it is a heading.  Anything BELOW this id is a
 -- person as far as ParseCredits is concerned.
-Credits.STAFF = defineString("STAFF", {
-  "      #MON",
-  "    GOLD VERSION",
-  "     PORT STAFF",
-})
+-- Credits_Staff differs per edition, including the centring spaces
+-- (data/credits_strings.asm:54-60).
+Credits.STAFF = defineString("STAFF",
+  require("src.core.GameVersion").get() == "silver" and {
+    "      #MON",
+    "   SILVER VERSION",
+    "     PORT STAFF",
+  } or {
+    "      #MON",
+    "    GOLD VERSION",
+    "     PORT STAFF",
+  })
 defineString("DIRECTOR", "      DIRECTOR")
 defineString("PROGRAMMING", "    PROGRAMMING")
 defineString("ENGINE_DESIGN", "   ENGINE DESIGN")