feat(mystery): mobile chip computation and rendering

Pure computeChips function (TDD, 4 tests) generates context-aware direction/item/encounter/meta chips from game state; chip-render.ts wires chips to DOM; terminal.ts calls refreshChips on init, each Enter dispatch, restart, and undo.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ui/chips.test.ts

@@ -0,0 +1,36 @@
+import { describe, it, expect } from 'vitest'
+import { computeChips } from './chips'
+import { world } from '../world'
+import { initialStateFor } from '../engine/dispatcher'
+import { dispatch } from '../engine/dispatcher'
+
+describe('computeChips — sample world', () => {
+  it('shows valid exits as direction chips with the dim flag for invalid ones', () => {
+    const s = initialStateFor(world)
+    const chips = computeChips(s, world)
+    const directions = chips.filter((c) => c.kind === 'direction')
+    expect(directions.find((c) => c.label.includes('N'))?.disabled).toBe(false)
+    expect(directions.find((c) => c.label.includes('S'))?.disabled).toBe(true)
+  })
+
+  it('adds TAKE chips for visible takeable items', () => {
+    const s = initialStateFor(world)
+    const chips = computeChips(s, world)
+    expect(chips.find((c) => c.kind === 'item' && c.command === 'take letter')).toBeTruthy()
+  })
+
+  it('adds an encounter verb chip when an encounter is active', () => {
+    let s = initialStateFor(world)
+    s = dispatch(s, { kind: 'go', direction: 'n' }, world).state
+    s = dispatch(s, { kind: 'go', direction: 'e' }, world).state
+    const chips = computeChips(s, world)
+    expect(chips.find((c) => c.kind === 'encounter' && c.command.includes('rat'))).toBeTruthy()
+  })
+
+  it('always includes LOOK and INV', () => {
+    const s = initialStateFor(world)
+    const chips = computeChips(s, world)
+    expect(chips.find((c) => c.command === 'look')).toBeTruthy()
+    expect(chips.find((c) => c.command === 'inventory')).toBeTruthy()
+  })
+})