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_launch_browser.md

@@ -0,0 +1,46 @@
+---
+name: pw_launch_browser
+kind: function
+lang: ts
+domain: browser
+version: "1.0.0"
+purity: impure
+signature: "async (opts?: PwLaunchOptions) => Promise<PwHandles>"
+description: "Launches chromium and returns a Page navigated to baseUrl. Optionally pre-authenticates via storageState. Used as the entry point for any Playwright e2e test in the registry."
+tags: [playwright, e2e, browser]
+uses_functions: []
+uses_types: []
+returns: []
+returns_optional: false
+error_type: "error_go_core"
+imports: []
+params:
+  - name: opts
+    desc: "Launch options; all fields optional with sensible defaults for kanban e2e."
+output: "Playwright handles {browser, context, page, close}; page is already navigated to baseUrl."
+tested: true
+tests: ["launch defaults", "launch with storageState", "close calls both"]
+test_file_path: "frontend/functions/browser/pw_launch_browser.test.ts"
+file_path: "frontend/functions/browser/pw_launch_browser.ts"
+---
+
+## Ejemplo
+
+```typescript
+import { pw_launch_browser } from "./pw_launch_browser";
+
+const h = await pw_launch_browser({ baseUrl: "http://localhost:5180", headless: false });
+await h.page.click("text=Login");
+await h.close();
+```
+
+## Cuando usarla
+
+Cuando necesites iniciar un test e2e de Playwright para el SPA de kanban (o cualquier frontend del registry). Es el primer paso de cualquier suite: abre el browser, navega al baseUrl y devuelve los handles listos para interactuar.
+
+## Gotchas
+
+- `playwright` es una peer dependency: debe estar instalada en el proyecto consumidor (`pnpm add -D playwright` o `npm i -D playwright`). El registry no la instala.
+- `storageStatePath` se ignora silenciosamente si el archivo no existe — verifica que el archivo de auth se haya generado antes de pasarlo.
+- `close()` cierra context primero y luego browser; no llames `browser.close()` manualmente antes de `close()` o el context quedara huerfano.
+- La navegacion a `baseUrl` ocurre dentro de `pw_launch_browser`; si el servidor no esta levantado, `page.goto` lanzara un error de red.