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.

CONTRIBUTING-mods.md

@@ -140,17 +140,17 @@ ship text.
 
 ### 4. `games` (and the legacy `gen2compat`)
 
-Pokemon Gold is Gen 2, and it runs its own battle engine, overworld, script
-VM and save format. The mod API is shared across both generations (same hook
-names, same event names, same registry names) but Gold cannot serve all of it
-yet, so Gen 2 is opt-in. Say which games the mod is for:
+Pokemon Gold and Silver are Gen 2, and they run their own battle engine,
+overworld, script VM and save format. The mod API is shared across both
+generations (same hook names, same event names, same registry names) but Gen 2
+cannot serve all of it yet, so it is opt-in. Say which games the mod is for:
 
 ```json
 "games": ["gen1", "gen2"]
 ```
 
-Each entry is a version id (`"red"`, `"blue"`, `"yellow"`, `"gold"`), a
-generation (`"gen1"`, `"gen2"`) or `"all"`;
+Each entry is a version id (`"red"`, `"blue"`, `"yellow"`, `"gold"`,
+`"silver"`), a generation (`"gen1"`, `"gen2"`) or `"all"`;
 `src/mods/ModTargets.lua` resolves them off `GameVersion.ORDER` so nothing
 restates the game list. `python3 tools/modkit.py scaffold my_mod --games
 gen1,gen2` writes the key for you. The mod still installs to one directory,
@@ -159,10 +159,10 @@ gen1,gen2` writes the key for you. The mod still installs to one directory,
 Absent means Gen 1 only, which is what every mod written before the key existed
 was tested as. `"gen2compat": true` is the legacy spelling, still accepted and
 purely additive (it *adds* the Gen 2 games), so no manifest can lose a game it
-already ran on. On a Gold boot a mod claiming no Gen 2 game is not loaded at
-all: the manager lists it as `ENABLED (NOT THIS GAME)` and says why, because a
-mod that half-applies reads as a broken mod. Claim Gen 2 once you have actually
-run your mod on Gold.
+already ran on. On a Gold or Silver boot a mod claiming no Gen 2 game is not
+loaded at all: the manager lists it as `ENABLED (NOT THIS GAME)` and says why,
+because a mod that half-applies reads as a broken mod. Claim Gen 2 once you
+have actually run your mod on Gold or Silver.
 
 Every token is enforced, per game: the loader gates on the same
 `ModTargets.supports` answer both mod surfaces draw, so `"games": ["blue"]`
@@ -173,7 +173,7 @@ before the key existed changes behavior; list both generations or say `"all"`
 when you mean everywhere.
 
 `docs/mod-api-gen2-compat.md` is the compatibility matrix: what works on Gold
-today (40 of the 46 registries, 40 event and 43 hook names shared with Gen 1,
+and Silver today (40 of the 46 registries, 40 event and 43 hook names shared with Gen 1,
 and 24 Gen 2-only ones), which registries have no Gen 2 home and drop their
 writes with a report, and which hooks and events are still to come.
 `docs/preparing-your-mod-for-gen2.md` is the step-by-step migration guide for a