fix: wrap GameOverScreen in ErrorBoundary and add defensive checks for day 30 blank page bug

- Wrap GameOverScreen in ErrorBoundary in page.tsx to prevent blank page on render errors
- Add defensive Number.isFinite checks in GameOverScreen for all numeric props
- Add regression test for day 30 → game-over flow (day30-blank-page.test.ts)

Fixes #375

src/lib/game/__tests__/day30-blank-page.test.ts

@@ -0,0 +1,207 @@
+import { describe, it, expect, beforeEach } from 'vitest';
+import { useGameStore } from '../stores/gameStore';
+import { useManaStore, makeInitialElements } from '../stores/manaStore';
+import { useCombatStore } from '../stores/combatStore';
+import { usePrestigeStore } from '../stores/prestigeStore';
+import { useUIStore } from '../stores/uiStore';
+import { useDisciplineStore } from '../stores/discipline-slice';
+import { useCraftingStore } from '../stores/craftingStore';
+import { useAttunementStore } from '../stores/attunementStore';
+import { HOURS_PER_TICK, MAX_DAY } from '../constants';
+import { getFloorMaxHP } from '../utils';
+import { fmt, formatHour } from '../utils/formatting';
+
+// ─── Full Store Reset ─────────────────────────────────────────────────────────
+
+function resetAllStores() {
+  useUIStore.setState({
+    paused: false,
+    gameOver: false,
+    victory: false,
+    logs: [],
+  });
+
+  useGameStore.setState({
+    day: 1,
+    hour: 0,
+    incursionStrength: 0,
+    containmentWards: 0,
+    initialized: true,
+  });
+
+  useManaStore.setState({
+    rawMana: 100,
+    meditateTicks: 0,
+    totalManaGathered: 0,
+    elements: makeInitialElements(50, {}),
+  });
+
+  useCombatStore.setState({
+    currentFloor: 1,
+    floorHP: getFloorMaxHP(1),
+    floorMaxHP: getFloorMaxHP(1),
+    maxFloorReached: 1,
+    activeSpell: 'manaBolt',
+    currentAction: 'meditate',
+    castProgress: 0,
+    spireMode: false,
+    currentRoom: { roomType: 'combat', enemies: [] },
+    clearedFloors: {},
+    climbDirection: null,
+    isDescending: false,
+    golemancy: { activeGolems: [], lastSummonFloor: 0, golemDesigns: {}, golemLoadout: [] },
+    equipmentSpellStates: [],
+    comboHitCount: 0,
+    floorHitCount: 0,
+    spells: { manaBolt: { learned: true, level: 1, studyProgress: 0 } },
+    activityLog: [],
+    achievements: { unlocked: [], progress: {} },
+    totalSpellsCast: 0,
+    totalDamageDealt: 0,
+    totalCraftsCompleted: 0,
+  });
+
+  usePrestigeStore.setState({
+    loopCount: 0,
+    insight: 0,
+    totalInsight: 0,
+    loopInsight: 0,
+    prestigeUpgrades: {},
+    pactSlots: 1,
+    defeatedGuardians: [],
+    signedPacts: [],
+    signedPactDetails: {},
+    pactRitualFloor: null,
+    pactRitualProgress: 0,
+  });
+
+  useDisciplineStore.setState({
+    disciplines: {},
+    activeIds: [],
+    concurrentLimit: 1,
+    totalXP: 0,
+  });
+
+  useCraftingStore.setState({
+    designs: {},
+    designProgress: 0,
+    designSlot2Active: false,
+    designProgress2: 0,
+    preparationProgress: 0,
+    applicationProgress: 0,
+    equipmentCraftingProgress: 0,
+    equipmentInstances: {},
+    equippedInstances: {},
+    lootInventory: { materials: {}, equipment: [], blueprints: [] },
+    unlockedEffects: [],
+    unlockedRecipes: [],
+    enchantmentPowerBonus: 0,
+  });
+
+  useAttunementStore.setState({
+    attunements: {
+      enchanter: { active: true, level: 1, xp: 0 },
+    },
+  });
+}
+
+// ═══════════════════════════════════════════════════════════════════════════════
+// DAY 30 BLANK PAGE BUG REPRODUCTION
+// ═══════════════════════════════════════════════════════════════════════════════
+
+describe('Day 30 Blank Page Bug', () => {
+  beforeEach(resetAllStores);
+
+  it('should not crash when setting day to 30 and running ticks to game over', () => {
+    // Reproduce: Debug panel sets day to 20, then day to 30
+    useGameStore.setState({ day: 20, hour: 0 });
+    useGameStore.setState({ day: 30, hour: 0 });
+
+    // Verify state is correct
+    expect(useGameStore.getState().day).toBe(30);
+    expect(useGameStore.getState().hour).toBe(0);
+    expect(useUIStore.getState().gameOver).toBe(false);
+
+    // Run ticks until game over (day > 30)
+    let ticks = 0;
+    const maxTicks = 1000;
+    while (!useUIStore.getState().gameOver && ticks < maxTicks) {
+      useGameStore.getState().tick();
+      ticks++;
+    }
+
+    // Game over should have triggered
+    expect(useUIStore.getState().gameOver).toBe(true);
+    expect(useUIStore.getState().victory).toBe(false);
+
+    // loopInsight should be a valid number (not undefined/NaN)
+    const loopInsight = usePrestigeStore.getState().loopInsight;
+    expect(typeof loopInsight).toBe('number');
+    expect(Number.isFinite(loopInsight)).toBe(true);
+
+    // day and hour should be valid
+    const day = useGameStore.getState().day;
+    const hour = useGameStore.getState().hour;
+    expect(typeof day).toBe('number');
+    expect(typeof hour).toBe('number');
+    expect(Number.isFinite(day)).toBe(true);
+    expect(Number.isFinite(hour)).toBe(true);
+
+    console.log(`Game over after ${ticks} ticks. Day=${day}, Hour=${hour}, LoopInsight=${loopInsight}`);
+  });
+
+  it('should produce valid GameOverScreen props after loop ends at day 30', () => {
+    // Set day to 30 directly (simulating debug panel)
+    useGameStore.setState({ day: 30, hour: 0 });
+
+    // Run ticks until game over
+    let ticks = 0;
+    const maxTicks = 1000;
+    while (!useUIStore.getState().gameOver && ticks < maxTicks) {
+      useGameStore.getState().tick();
+      ticks++;
+    }
+
+    expect(useUIStore.getState().gameOver).toBe(true);
+
+    // These are the exact props passed to GameOverScreen in page.tsx
+    const day = useGameStore.getState().day;
+    const hour = useGameStore.getState().hour;
+    const loopInsight = usePrestigeStore.getState().loopInsight;
+    const insight = usePrestigeStore.getState().insight;
+
+    // All must be finite numbers for fmt() and formatHour() to work
+    expect(Number.isFinite(day)).toBe(true);
+    expect(Number.isFinite(hour)).toBe(true);
+    expect(Number.isFinite(loopInsight)).toBe(true);
+    expect(Number.isFinite(insight)).toBe(true);
+
+    // fmt() should not throw
+    expect(() => fmt(loopInsight)).not.toThrow();
+    expect(() => fmt(insight)).not.toThrow();
+
+    // formatHour() should not throw
+    expect(() => formatHour(hour)).not.toThrow();
+  });
+
+  it('should handle game over when jumping from day 20 to day 30 with incursion', () => {
+    // Set up a more realistic state with some progress
+    useManaStore.setState({ rawMana: 500, totalManaGathered: 10000 });
+    useCombatStore.setState({ maxFloorReached: 50 });
+
+    // Jump to day 20, then day 30
+    useGameStore.setState({ day: 20, hour: 0 });
+    useGameStore.setState({ day: 30, hour: 0 });
+
+    // Run ticks until game over
+    let ticks = 0;
+    const maxTicks = 1000;
+    while (!useUIStore.getState().gameOver && ticks < maxTicks) {
+      useGameStore.getState().tick();
+      ticks++;
+    }
+
+    expect(useUIStore.getState().gameOver).toBe(true);
+    expect(usePrestigeStore.getState().loopInsight).toBeGreaterThan(0);
+  });
+});