feat(registry): add playwright capability group (6 TS browser fns)

New domain `browser` under frontend/functions/ with 6 Playwright helpers:
- pw_launch_browser: chromium + context + page bootstrap with storageState
  support and baseUrl navigation.
- pw_kanban_login: authenticates a Page against /api/auth/login; sets the
  kanban_session cookie via shared storageState; verifies login page no
  longer visible after navigation.
- pw_drag_drop: human-like pointer drag (mousedown + activateOffset +
  stepped move + mouseup) compatible with @dnd-kit/core's 8px activation
  threshold; supports hoverMs for time-based dropzones.
- pw_keyboard_sequence: ordered focus/type/press/wait steps for scripting
  realistic input flows (typing then arrow-key navigating autocompletes).
- pw_wait_predicate: thin wrapper over page.waitForFunction with friendlier
  defaults and custom error messages.
- pw_assert_class: poll-based assertion that a Locator has/lacks a CSS
  class within a timeout; useful for visual-state checks.

Each function ships with vitest tests (5-8 cases each) covering both happy
and error paths, plus self-documenting .md (Ejemplo + Cuando usarla +
Gotchas + frontmatter with params/output schema).

Adds frontend/functions/package.json with `"type": "module"` so consumers
can ESM-import the .ts files from anywhere in the registry (Playwright's
tsx loader respects nearest package.json).

Capability page docs/capabilities/playwright.md documents the group with
a canonical end-to-end example, frontiers, prerequisites, and gotchas.
Index updated.

First consumer (issue 0088): apps/kanban requester-input.spec.ts.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/functions/browser/pw_assert_class.md

@@ -0,0 +1,69 @@
+---
+name: pw_assert_class
+kind: function
+lang: ts
+domain: browser
+version: "1.0.0"
+purity: impure
+signature: "async (page: Page, opts: PwAssertClassOptions) => Promise<void>"
+description: "Asserts a Playwright Locator has (or lacks) a given CSS class, with polling up to timeoutMs. Use for visual-state checks like red borders, highlight pulses, active tabs."
+tags: [playwright, e2e, browser, assert]
+uses_functions: []
+uses_types: []
+returns: []
+returns_optional: false
+error_type: "error_go_core"
+imports: []
+params:
+  - name: page
+    desc: "Playwright Page."
+  - name: opts
+    desc: "{selector, className, mustHave?, timeoutMs?}. selector accepts string CSS or Locator. className without leading dot."
+output: "void; throws with detailed message on timeout."
+tested: true
+tests: ["has class passes", "lacks class passes", "timeout error message", "string selector resolves", "locator polled"]
+test_file_path: "frontend/functions/browser/pw_assert_class.test.ts"
+file_path: "frontend/functions/browser/pw_assert_class.ts"
+---
+
+## Ejemplo
+
+```typescript
+import { pw_assert_class } from "./pw_assert_class";
+
+// Assert card has red border class after max-time exceeded
+await pw_assert_class(page, {
+  selector: "[data-card-id='abc']",
+  className: "border-red",
+  mustHave: true,
+  timeoutMs: 3000,
+});
+
+// Assert roulette animation class is active on a card Locator
+const card = page.locator(".kanban-card").first();
+await pw_assert_class(page, {
+  selector: card,
+  className: "highlight-pulse",
+  mustHave: true,
+  timeoutMs: 2000,
+});
+
+// Assert class is NOT present after animation ends
+await pw_assert_class(page, {
+  selector: card,
+  className: "highlight-pulse",
+  mustHave: false,
+});
+```
+
+## Cuando usarla
+
+Cuando necesites verificar que un elemento tiene (o no tiene) una clase CSS concreta en un test e2e de Playwright — por ejemplo comprobar que una tarjeta tiene `border-red` cuando se supera su tiempo máximo, o que `highlight-pulse` está activo durante la animación de ruleta. Úsala después de disparar la acción que debería cambiar el estado visual y antes de continuar con el siguiente paso del test.
+
+## Gotchas
+
+- Si `selector` es un string, usa `page.waitForFunction` internamente (delegado a la página), lo que es eficiente pero requiere que el selector sea un CSS selector válido para `document.querySelector`.
+- Si `selector` es un `Locator`, usa un bucle de polling con `locator.evaluate()`. Los Locators no se pueden serializar a través del contexto de `waitForFunction`.
+- `timeoutMs` por defecto es 5000 ms — ajústalo si la animación o transición tarda más.
+- Las clases se comprueban con `classList.contains(className)` — no incluyas el punto inicial.
+- Si el elemento está desconectado del DOM durante el polling de un Locator, se trata como condición no cumplida y sigue reintentando hasta el timeout.