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_drag_drop.md

@@ -0,0 +1,52 @@
+---
+name: pw_drag_drop
+kind: function
+lang: ts
+domain: browser
+version: "1.0.0"
+purity: impure
+signature: "async (page: Page, opts: PwDragDropOptions) => Promise<void>"
+description: "Simulates a human pointer drag in Playwright compatible with dnd-kit (PointerEvents + 8px activation threshold). Uses stepped mousemove with configurable pacing. Supports hoverMs for time-based dropzones (e.g. sidebar auto-open after 400ms hover)."
+tags: [playwright, e2e, browser, drag]
+uses_functions: []
+uses_types: []
+returns: []
+returns_optional: false
+error_type: "error_go_core"
+imports: []
+params:
+  - name: page
+    desc: "Playwright Page."
+  - name: opts
+    desc: "{source, target, steps?, delayMs?, hoverMs?, activateOffset?}. source/target accept selector string or Locator."
+output: "void; performs full pointer drag from source center to target center."
+tested: true
+tests: ["happy path", "no source bbox throws", "no target bbox throws", "hoverMs adds wait", "string selectors resolve"]
+test_file_path: "frontend/functions/browser/pw_drag_drop.test.ts"
+file_path: "frontend/functions/browser/pw_drag_drop.ts"
+---
+
+## Ejemplo
+
+```typescript
+import { pw_drag_drop } from "./pw_drag_drop";
+
+await pw_drag_drop(page, {
+  source: "[data-card-id='abc']",
+  target: "[data-column-id='xyz']",
+  hoverMs: 500,
+});
+```
+
+## Cuando usarla
+
+Cuando necesites arrastrar un elemento en el browser durante un test e2e con Playwright y el target usa `@dnd-kit/core`. El `dragTo` nativo de Playwright emite eventos HTML5 drag que dnd-kit ignora; esta funcion usa la API de mouse raw con un movimiento de activacion inicial para cruzar el umbral de 8px de dnd-kit.
+
+## Gotchas
+
+- `playwright` es una peer dependency: debe estar instalada en el proyecto consumidor (`pnpm add -D playwright`). El registry no la instala.
+- El umbral de activacion de dnd-kit es configurable en el `PointerSensor`; si el proyecto usa un umbral distinto al default de 8px, ajustar `activateOffset` (default: `{x: 12, y: 0}`) para superarlo.
+- `steps` y `delayMs` controlan la suavidad del drag. Valores bajos (steps=5, delayMs=0) pueden hacer que dnd-kit no detecte el movimiento como drag en versiones antiguas; los defaults (20 steps, 16ms) simulan ~60fps.
+- `hoverMs` es util para dropzones que se abren al mantener hover durante un tiempo (ej. sidebar de kanban que se abre tras 400ms). Pasarlo en 0 omite la espera.
+- Los source/target deben ser visibles y tener bounding box; si no se encuentran (display:none, detached) la funcion lanza un error descriptivo.
+- `activateOffset` es relativo al centro del source, no a su esquina.