Big, tough bosses; working machines show it; JEI drop pages on the roadmap

Bosses (Adrian, 2026-11-02: Eternatus too small and too easy; guardians way
bigger and tougher; only defensive stats up; no attack takes more than 25 %):
- Guardians scale to about 8 blocks tall (1.5x-12x), Eternatus to 15 blocks
  (2.5x, was 0.2x). Cave guardians look for a spot with room above them.
  Bosses already in a world grow on the next check outside battle.
- Perfect IVs and 170 EVs each in HP, Defense and Sp. Def, nothing offensive.
- The Guardian's Ward, a Showdown-only held item (held_items/guardiansward.js)
  handed to every boss by a HeldItemProvider: Defense and Sp. Def x2 while
  defending, and one attack (all hits together) takes at most 25 % of max HP.
- Area attacks that start at the boss reach half its width further.

Machines (Adrian, 2026-11-02): a working core is active: it glows, its front
animates (flickering fire on the furnace core, pulsing emblems elsewhere), and
particles show in the chamber and at the core (client side). The Pokemon
inside flinches about every 15 s (red flash, Cobblemon's hit sound, no damage).

Roadmap Phase 8: every item that can drop gets a JEI page naming its sources.

Self-tests: practice_bosses_spawn checks size and training,
boss_takes_a_quarter_per_attack runs a real battle (each Lv 100 Bullet Seed
takes exactly a quarter), heat_core_cooks_with_hoppers checks the active state
and the flinch. Self-tests and the island check pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

mod/src/main/kotlin/dev/cobblesurvival/selftest/MachineTests.kt

@@ -247,7 +247,17 @@ object MachineTests {
         level.setBlockAndUpdate(furnace.below(), Blocks.HOPPER.defaultBlockState().setValue(HopperBlock.FACING, Direction.DOWN))
         (level.getBlockEntity(furnace.above()) as HopperBlockEntity).setItem(0, ItemStack(Items.RAW_IRON, 4))
         val output = level.getBlockEntity(furnace.below()) as HopperBlockEntity
+        val active = { core.blockState.getValue(MachineBlock.ACTIVE) }
         s.helper.startSequence()
+            // Adrian, 2026-11-02: a working machine shows it (the core glows and animates, particles show).
+            .thenWaitUntil { s.check(active()) { "the Large Furnace's core doesn't show that it works" } }
+            .thenExecute {
+                // The Pokémon inside flinches as if hit, but takes no damage.
+                val shown = displays(level, core.blockPos).firstOrNull() ?: throw GameTestAssertException("no Pokémon shown in the chamber")
+                MachineDisplay.flinch(level, shown)
+                val inside = core.pokemon!!
+                s.check(shown.isAlive && inside.currentHealth == inside.maxHealth) { "a flinch hurt the Pokémon (${inside.currentHealth}/${inside.maxHealth})" }
+            }
             .thenWaitUntil {
                 val ingots = (0 until output.containerSize).sumOf { output.getItem(it).takeIf { s -> s.`is`(Items.IRON_INGOT) }?.count ?: 0 }
                 s.check(ingots >= 4) { "the hopper under the furnace has $ingots iron ingots, not 4" }
@@ -256,6 +266,7 @@ object MachineTests {
                 val fuel = (level.getBlockEntity(furnace) as AbstractFurnaceBlockEntity).getItem(1)
                 s.check(fuel.isEmpty) { "the furnace got fuel: $fuel" }
             }
+            .thenWaitUntil { s.check(!active()) { "the Large Furnace's core still shows work with nothing left to cook" } }
             .thenSucceed()
     }