fix: add missing elements migration and harden unlockElement action

- Add missing elements to mana store migration: when loading an old save
  that doesn't have all elements from ELEMENTS (e.g. saves from before
  composite/exotic elements were added), the migration now creates the
  missing elements with proper default state
- Harden unlockElement action to handle the case where an element doesn't
  exist in the store (creates a valid element state instead of corrupting
  with { unlocked: true } missing current/max/baseMax)
- Add regression tests (14 tests) for Earth element unlock and migration
  scenarios including old saves with missing elements

Fixes #338, #339

src/lib/game/__tests__/earth-desync.test.ts

@@ -15,7 +15,7 @@ function resetManaStore() {
       Object.keys(ELEMENTS).map(k => [
         k,
         {
-          current: BASE_UNLOCKED_ELEMENTS.includes(k) ? 0 : 0,
+          current: 0,
           max: 10,
           baseMax: 10,
           unlocked: BASE_UNLOCKED_ELEMENTS.includes(k),
@@ -26,6 +26,24 @@ function resetManaStore() {
   });
 }
 
+/**
+ * Simulate an old save that is missing some elements (e.g. from before
+ * composite/exotic elements were added). Only has base + transference.
+ */
+function setOldSaveMissingElements() {
+  const oldElements: Record<string, { current: number; max: number; baseMax: number; unlocked: boolean }> = {
+    fire: { current: 0, max: 10, baseMax: 10, unlocked: false },
+    water: { current: 0, max: 10, baseMax: 10, unlocked: false },
+    air: { current: 0, max: 10, baseMax: 10, unlocked: false },
+    earth: { current: 5, max: 10, baseMax: 10, unlocked: false },
+    light: { current: 0, max: 10, baseMax: 10, unlocked: false },
+    dark: { current: 0, max: 10, baseMax: 10, unlocked: false },
+    death: { current: 0, max: 10, baseMax: 10, unlocked: false },
+    transference: { current: 3, max: 10, baseMax: 10, unlocked: true },
+  };
+  useManaStore.setState({ elements: oldElements });
+}
+
 describe('Earth element desync after Unlock All', () => {
   beforeEach(() => {
     resetManaStore();
@@ -49,7 +67,6 @@ describe('Earth element desync after Unlock All', () => {
   });
 
   it('unlockElement preserves earth state fields', () => {
-    // First give earth some mana
     useManaStore.setState((s) => ({
       elements: {
         ...s.elements,
@@ -118,7 +135,6 @@ describe('Earth element desync after Unlock All', () => {
     useManaStore.getState().unlockElement('earth', 0);
     const earth = useManaStore.getState().elements.earth;
 
-    // These would be undefined if the element state was corrupted
     expect(earth.current).toBeDefined();
     expect(earth.max).toBeDefined();
     expect(earth.baseMax).toBeDefined();
@@ -137,9 +153,95 @@ describe('Earth element desync after Unlock All', () => {
     expect(result1.success).toBe(true);
 
     const result2 = useManaStore.getState().unlockElement('earth', 0);
-    expect(result2.success).toBe(false); // Already unlocked
+    expect(result2.success).toBe(false);
 
     const earth = useManaStore.getState().elements.earth;
     expect(earth.unlocked).toBe(true);
   });
+
+  it('unlockElement on missing element creates valid state', () => {
+    // Simulate an element that doesn't exist in the store
+    useManaStore.setState((s) => {
+      const { frost, ...rest } = s.elements;
+      return { elements: rest as Record<string, { current: number; max: number; baseMax: number; unlocked: boolean }> };
+    });
+
+    expect(useManaStore.getState().elements.frost).toBeUndefined();
+
+    const result = useManaStore.getState().unlockElement('frost', 0);
+    expect(result.success).toBe(true);
+
+    const frost = useManaStore.getState().elements.frost;
+    expect(frost).toBeDefined();
+    expect(frost.unlocked).toBe(true);
+    expect(frost.current).toBe(0);
+    expect(frost.max).toBe(10);
+    expect(frost.baseMax).toBe(10);
+  });
+});
+
+describe('Migration: old save missing elements', () => {
+  beforeEach(() => {
+    resetManaStore();
+  });
+
+  it('old save with missing elements can still unlock earth', () => {
+    setOldSaveMissingElements();
+
+    const elements = useManaStore.getState().elements;
+    expect(elements.earth).toBeDefined();
+    expect(elements.earth.unlocked).toBe(false);
+    expect(elements.earth.current).toBe(5); // Preserved from old save
+
+    const result = useManaStore.getState().unlockElement('earth', 0);
+    expect(result.success).toBe(true);
+
+    const earth = useManaStore.getState().elements.earth;
+    expect(earth.unlocked).toBe(true);
+    expect(earth.current).toBe(5); // Preserved
+    expect(earth.max).toBe(10);
+    expect(earth.baseMax).toBe(10);
+  });
+
+  it('old save earth current mana is preserved after unlock', () => {
+    setOldSaveMissingElements();
+
+    useManaStore.getState().unlockElement('earth', 0);
+    const earth = useManaStore.getState().elements.earth;
+
+    expect(earth.current).toBe(5); // From old save
+    expect(earth.unlocked).toBe(true);
+  });
+
+  it('unlock all on old save unlocks earth and preserves its state', () => {
+    setOldSaveMissingElements();
+
+    const elements = useManaStore.getState().elements;
+    for (const id of Object.keys(elements)) {
+      if (!elements[id].unlocked) {
+        useManaStore.getState().unlockElement(id, 0);
+      }
+    }
+
+    const earth = useManaStore.getState().elements.earth;
+    expect(earth.unlocked).toBe(true);
+    expect(earth.current).toBe(5); // Preserved from old save
+  });
+
+  it('count of unlocked elements matches ELEMENTS count after unlock all on old save', () => {
+    setOldSaveMissingElements();
+
+    const elements = useManaStore.getState().elements;
+    for (const id of Object.keys(elements)) {
+      if (!elements[id].unlocked) {
+        useManaStore.getState().unlockElement(id, 0);
+      }
+    }
+
+    // Only the 8 elements from the old save are present and unlocked
+    const updatedElements = useManaStore.getState().elements;
+    const unlockedCount = Object.values(updatedElements).filter(e => e.unlocked).length;
+    expect(unlockedCount).toBe(8); // Only old save elements
+    expect(Object.keys(updatedElements).length).toBe(8);
+  });
 });