feat: quick slots with 1-4 hotkeys (Phase 4.6)

4 quick slots bound to keys 1-4. Active slot determines what F key
throws. Auto-assigns new items on collection. Clears slot when item
depleted. 15 new tests (213 total).

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/quickslots.test.ts

@@ -0,0 +1,131 @@
+/**
+ * Quick Slots Tests — Phase 4.6
+ *
+ * Tests: slot assignment, active selection, key switching.
+ */
+
+import { describe, it, expect } from 'vitest';
+import { QuickSlots, SLOT_COUNT } from '../src/player/quickslots';
+
+describe('QuickSlots — creation', () => {
+  it('starts with all slots empty', () => {
+    const qs = new QuickSlots();
+    for (let i = 0; i < SLOT_COUNT; i++) {
+      expect(qs.getSlot(i)).toBeNull();
+    }
+  });
+
+  it('starts with slot 0 active', () => {
+    const qs = new QuickSlots();
+    expect(qs.activeIndex).toBe(0);
+  });
+
+  it('has 4 slots', () => {
+    expect(SLOT_COUNT).toBe(4);
+    const qs = new QuickSlots();
+    expect(qs.getAll()).toHaveLength(4);
+  });
+});
+
+describe('QuickSlots — assignment', () => {
+  it('assigns item to slot', () => {
+    const qs = new QuickSlots();
+    qs.assign(0, 'Na');
+    expect(qs.getSlot(0)).toBe('Na');
+  });
+
+  it('replaces existing item in slot', () => {
+    const qs = new QuickSlots();
+    qs.assign(0, 'Na');
+    qs.assign(0, 'Fe');
+    expect(qs.getSlot(0)).toBe('Fe');
+  });
+
+  it('clears slot with null', () => {
+    const qs = new QuickSlots();
+    qs.assign(0, 'Na');
+    qs.assign(0, null);
+    expect(qs.getSlot(0)).toBeNull();
+  });
+
+  it('ignores invalid index', () => {
+    const qs = new QuickSlots();
+    qs.assign(-1, 'Na');
+    qs.assign(4, 'Na');
+    // No crash, no change
+    expect(qs.getAll()).toEqual([null, null, null, null]);
+  });
+});
+
+describe('QuickSlots — active slot', () => {
+  it('returns active slot item', () => {
+    const qs = new QuickSlots();
+    qs.assign(0, 'Na');
+    expect(qs.getActive()).toBe('Na');
+  });
+
+  it('returns null for empty active slot', () => {
+    const qs = new QuickSlots();
+    expect(qs.getActive()).toBeNull();
+  });
+
+  it('switches active slot', () => {
+    const qs = new QuickSlots();
+    qs.assign(0, 'Na');
+    qs.assign(1, 'Fe');
+    qs.assign(2, 'Cu');
+
+    qs.setActive(1);
+    expect(qs.activeIndex).toBe(1);
+    expect(qs.getActive()).toBe('Fe');
+
+    qs.setActive(2);
+    expect(qs.getActive()).toBe('Cu');
+  });
+
+  it('clamps active index to valid range', () => {
+    const qs = new QuickSlots();
+    qs.setActive(-1);
+    expect(qs.activeIndex).toBe(0);
+
+    qs.setActive(10);
+    expect(qs.activeIndex).toBe(3);
+  });
+});
+
+describe('QuickSlots — getAll', () => {
+  it('returns snapshot of all slots', () => {
+    const qs = new QuickSlots();
+    qs.assign(0, 'Na');
+    qs.assign(2, 'Fe');
+    expect(qs.getAll()).toEqual(['Na', null, 'Fe', null]);
+  });
+});
+
+describe('QuickSlots — auto-assign', () => {
+  it('assigns to first empty slot', () => {
+    const qs = new QuickSlots();
+    qs.assign(0, 'Na');
+    const index = qs.autoAssign('Fe');
+    expect(index).toBe(1);
+    expect(qs.getSlot(1)).toBe('Fe');
+  });
+
+  it('returns -1 when all slots full', () => {
+    const qs = new QuickSlots();
+    qs.assign(0, 'Na');
+    qs.assign(1, 'Fe');
+    qs.assign(2, 'Cu');
+    qs.assign(3, 'S');
+    const index = qs.autoAssign('H');
+    expect(index).toBe(-1);
+  });
+
+  it('does not duplicate item already in a slot', () => {
+    const qs = new QuickSlots();
+    qs.assign(0, 'Na');
+    const index = qs.autoAssign('Na');
+    expect(index).toBe(-1); // already assigned
+    expect(qs.getAll().filter(s => s === 'Na')).toHaveLength(1);
+  });
+});