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_keyboard_sequence.ts

@@ -0,0 +1,50 @@
+import type { Page } from "playwright";
+
+/**
+ * A single step in a keyboard interaction sequence.
+ *
+ * - `focus`  — focuses a DOM element via CSS selector.
+ * - `type`   — types text character by character with a humanlike delay.
+ * - `press`  — sends a single named key (e.g. "ArrowDown", "Enter", "Escape", "Tab").
+ * - `wait`   — pauses execution for the given number of milliseconds.
+ */
+export type KbStep =
+  | { kind: "focus"; selector: string }
+  | { kind: "type"; text: string; delayMs?: number }
+  | { kind: "press"; key: string }
+  | { kind: "wait"; ms: number };
+
+/**
+ * pw_keyboard_sequence — executes an ordered sequence of keyboard interactions on a Playwright Page.
+ *
+ * Use to script realistic input flows such as typing into an autocomplete field and then
+ * navigating its dropdown with arrow keys before pressing Enter.
+ */
+export async function pw_keyboard_sequence(
+  page: Page,
+  sequence: KbStep[]
+): Promise<void> {
+  for (const step of sequence) {
+    switch (step.kind) {
+      case "focus":
+        await page.locator(step.selector).first().focus();
+        break;
+      case "type":
+        await page.keyboard.type(step.text, { delay: step.delayMs ?? 30 });
+        break;
+      case "press":
+        await page.keyboard.press(step.key);
+        break;
+      case "wait":
+        await page.waitForTimeout(step.ms);
+        break;
+      default: {
+        // TypeScript exhaustiveness check — will also throw at runtime for JS callers.
+        const _exhaustive: never = step;
+        throw new Error(
+          `pw_keyboard_sequence: unknown step kind "${(step as KbStep & { kind: string }).kind}"`
+        );
+      }
+    }
+  }
+}