Add admin.js test coverage (100%) and update CLAUDE.md coverage rule

- Add admin.test.js with 3 tests: confirm cancel, confirm accept, no data-confirm
- Update CLAUDE.md: coverage rule includes PHP and JS

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/js/admin.test.js

@@ -0,0 +1,67 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+describe('admin.js', () => {
+    beforeEach(() => {
+        document.body.innerHTML = ''
+        vi.restoreAllMocks()
+        window.confirm = vi.fn()
+    })
+
+    it('prevents form submit when confirm is cancelled', async () => {
+        document.body.innerHTML = `
+            <form data-confirm="Are you sure?">
+                <button type="submit">Delete</button>
+            </form>
+        `
+
+        window.confirm.mockReturnValue(false)
+
+        await import('../../assets/admin.js')
+        document.dispatchEvent(new Event('DOMContentLoaded'))
+
+        const form = document.querySelector('form')
+        const event = new Event('submit', { cancelable: true })
+        form.dispatchEvent(event)
+
+        expect(window.confirm).toHaveBeenCalledWith('Are you sure?')
+        expect(event.defaultPrevented).toBe(true)
+    })
+
+    it('allows form submit when confirm is accepted', async () => {
+        document.body.innerHTML = `
+            <form data-confirm="Are you sure?">
+                <button type="submit">Delete</button>
+            </form>
+        `
+
+        window.confirm.mockReturnValue(true)
+
+        await import('../../assets/admin.js')
+        document.dispatchEvent(new Event('DOMContentLoaded'))
+
+        const form = document.querySelector('form')
+        const event = new Event('submit', { cancelable: true })
+        form.dispatchEvent(event)
+
+        expect(window.confirm).toHaveBeenCalledWith('Are you sure?')
+        expect(event.defaultPrevented).toBe(false)
+    })
+
+    it('does nothing on forms without data-confirm', async () => {
+        document.body.innerHTML = `
+            <form>
+                <button type="submit">Submit</button>
+            </form>
+        `
+
+        await import('../../assets/admin.js')
+        document.dispatchEvent(new Event('DOMContentLoaded'))
+
+        const form = document.querySelector('form')
+        const event = new Event('submit', { cancelable: true })
+        form.dispatchEvent(event)
+
+        expect(window.confirm).not.toHaveBeenCalled()
+        expect(event.defaultPrevented).toBe(false)
+    })
+})