shiny Pokemon, on by default

Gen 1 has no shininess of its own, but it has the four DVs Gen 2 reads to
decide it -- and the engine already ships that reading (Stats.isShiny, its
own comment calling it "the RBY virtual shiny", allowlisted for mods
precisely so an indicator mod can call it). Nothing new is stored on a
Pokemon and nothing migrates: every save already contains the answer, and
this starts drawing it. Random DVs land on the pattern 1 in 8192, which is
the classic rate and the default the odds dial ships at.

Deriving rather than storing is what makes it survive a save, a box, a
trade and an evolution with no second copy of the truth to drift. mon.shiny
is a cache written from the DVs, never read as the source.

The roll goes in Pokemon.new -- every wild, gift, starter and traded mon is
built there, and it is before the battle bakes its sprite, which
battle.started is already too late for. It draws from the mod's own random
stream so installing this does not shift the sequence damage rolls and
encounter slots come out of. Trainers stay ordinary by themselves: the
engine pins their DVs, as the real games do.

The models are genuinely recoloured, as part of the extraction. Each
species is decoded once, packed as usual, then recoloured and packed again
as NNNs.dsm. The colours are Stadium's own HSL slide (hue in degrees,
saturation and lightness on a -8..+8 scale at 12.5% a step); five species
carry an explicit colour table instead, because Stadium gives them a real
alternate texture that no single slide reproduces -- Jigglypuff's body must
stay pink while its irises rotate to green.

Extraction is the right moment because StadiumFx's generated frames are
still marked there and the packer drops the marker: it is the last point a
flame is distinguishable from a hide. A shiny Charizard has a shiny hide
and an ordinary fire. The normal packs are written BEFORE the recolour, so
they come out byte-identical and stadium_extract_test still diffs all 151
against the Python oracle unchanged -- no format change, no DSM4, no second
implementation to keep in step. REV goes to 3 so an existing cache rebuilds.

Flat art is tinted instead, because the engine bakes a species palette into
a cache with no notion of which individual is drawn. The tint comes from
that species' own slide rather than a generic gold. A multiply can only
darken, so species whose shiny is lighter read quieter there than on the
model; the status page's star is the mode-proof mark.

Tests: 58 assertions in tests/shiny_test.lua, including the colour
transform against 640 real colour pairs lifted from the verified texture
set, the DV model, the read side, and the end-to-end through the engine's
own constructor. stadium_extract_test gains --mod (worktrees have neither
the ROM nor the packs, both gitignored) and now also checks that every
shiny pack is the same length as its twin and actually differs.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

main.lua

@@ -88,6 +88,8 @@ local WorldCurve = V.require("WorldCurve")
 local ViewBox = V.require("ViewBox")
 local OverworldBattle = V.require("OverworldBattle")
 local BattleExit = V.require("BattleExit")
+local ShinyBattle = V.require("ShinyBattle")
+local ShinyUI = V.require("ShinyUI")
 local DayNight = V.require("DayNight")
 local DayTint = V.require("DayTint")
 local Water = V.require("Water")
@@ -1107,6 +1109,39 @@ end
 -- so this file keeps naming every engine seam the mod touches.
 OverworldBattle.install()
 
+-- ------- shiny Pokemon
+--
+-- ON, always, with no row to switch it off: shininess is a property of the
+-- Pokemon rather than a display mode, and a Pokemon that is shiny in one
+-- player's save and not another's is not a Pokemon, it is a setting.
+--
+-- It rests on a fact the engine already ships. Gen 1 has no shininess of its
+-- own, but it has the four DVs Gen 2 reads to decide it, and
+-- src/pokemon/Stats.lua:90 carries that reading -- the engine's own comment
+-- calls it "the RBY virtual shiny" and says it is there for indicator mods.
+-- So nothing new is stored on a Pokemon and nothing has to migrate: every
+-- save ever made already contains the answer, and this only starts drawing
+-- it. See lib/Shiny.lua for why deriving beats storing.
+--
+-- Three seams, each in its own file with its own reasoning:
+--   ShinyBattle  wraps Pokemon.new, which is where every wild, gift,
+--                starter and traded mon is built, so the roll lands before
+--                the sprite is baked
+--   ShinyUI      the battle pics' tint and the status page's mark
+--   ShinyFx      the arrival sparkle (armed from Stadium.update)
+--
+-- The Stadium models need no seam here at all: their recolour happens at
+-- extraction (lib/StadiumBuild.lua), and the battle simply asks for the
+-- shiny pack.
+ShinyBattle.install()
+ShinyUI.install()
+
+-- A save opened for the first time under this mod has shiny Pokemon in it
+-- already -- they always did -- so refresh the cached flag across the party
+-- rather than leaving it absent until each mon next changes.
+mod.events:on("save.loaded", function() ShinyBattle.markParty() end)
+mod.events:on("save.created", function() ShinyBattle.markParty() end)
+
 -- ------- the free-roam rungs' inputs and their walk
 --
 -- 1ST and 3RD need two things no other rung does, and each is a named seam.