feat(web): make Codex exploration collapse configurable (#1352)

* feat(web): configure Codex exploration collapse

Default Codex exploration groups to collapsed and expose a persisted chat setting for users who prefer them expanded.\n\nvia [HAPI](https://hapi.run)\n\nCo-Authored-By: HAPI <noreply@hapi.run>

* test(web): cover Codex exploration preference

Cover preference persistence, default cleanup, and cross-tab storage synchronization.\n\nvia [HAPI](https://hapi.run)\n\nCo-Authored-By: HAPI <noreply@hapi.run>

web/src/hooks/useCodexExplorationCollapse.test.ts

@@ -0,0 +1,78 @@
+import { act, renderHook } from '@testing-library/react'
+import { beforeEach, describe, expect, it } from 'vitest'
+import {
+    DEFAULT_CODEX_EXPLORATION_COLLAPSED,
+    getInitialCodexExplorationCollapsed,
+    useCodexExplorationCollapse,
+} from './useCodexExplorationCollapse'
+
+const STORAGE_KEY = 'hapi-codex-exploration-collapsed'
+
+describe('useCodexExplorationCollapse helpers', () => {
+    beforeEach(() => {
+        window.localStorage.clear()
+    })
+
+    it('defaults to collapsed', () => {
+        expect(getInitialCodexExplorationCollapsed()).toBe(DEFAULT_CODEX_EXPLORATION_COLLAPSED)
+    })
+
+    it('reads valid stored values and ignores invalid values', () => {
+        window.localStorage.setItem(STORAGE_KEY, 'false')
+        expect(getInitialCodexExplorationCollapsed()).toBe(false)
+
+        window.localStorage.setItem(STORAGE_KEY, 'invalid')
+        expect(getInitialCodexExplorationCollapsed()).toBe(DEFAULT_CODEX_EXPLORATION_COLLAPSED)
+    })
+})
+
+describe('useCodexExplorationCollapse', () => {
+    beforeEach(() => {
+        window.localStorage.clear()
+    })
+
+    it('persists the expanded preference', () => {
+        const { result } = renderHook(() => useCodexExplorationCollapse())
+
+        act(() => {
+            result.current.setCodexExplorationCollapsed(false)
+        })
+
+        expect(result.current.codexExplorationCollapsed).toBe(false)
+        expect(window.localStorage.getItem(STORAGE_KEY)).toBe('false')
+    })
+
+    it('removes the stored preference when restored to the default', () => {
+        window.localStorage.setItem(STORAGE_KEY, 'false')
+        const { result } = renderHook(() => useCodexExplorationCollapse())
+
+        act(() => {
+            result.current.setCodexExplorationCollapsed(true)
+        })
+
+        expect(result.current.codexExplorationCollapsed).toBe(true)
+        expect(window.localStorage.getItem(STORAGE_KEY)).toBeNull()
+    })
+
+    it('applies cross-tab changes from storage events', () => {
+        const { result } = renderHook(() => useCodexExplorationCollapse())
+
+        act(() => {
+            window.dispatchEvent(new StorageEvent('storage', {
+                key: STORAGE_KEY,
+                newValue: 'false',
+            }))
+        })
+
+        expect(result.current.codexExplorationCollapsed).toBe(false)
+
+        act(() => {
+            window.dispatchEvent(new StorageEvent('storage', {
+                key: STORAGE_KEY,
+                newValue: null,
+            }))
+        })
+
+        expect(result.current.codexExplorationCollapsed).toBe(true)
+    })
+})