feat(qa): add Playwright MCP test agents & config

Introduces Playwright testing agents (planner, generator, healer) powered by MCP to plan, generate, and heal end-to-end tests.

Configures the MCP server and integrates agent workflows into OpenCode and GitHub chat modes to enable AI-assisted testing.

Adds Playwright test dependency and updates lockfile; adjusts markdown lint ignores to reduce noise.

Adds contributor guidance for Claude Code to streamline local development.

Normalizes shell script shebangs to use /usr/bin/env bash for portability.

Enables automated browser testing workflows and resilient test maintenance within AI-enabled tooling.

.scripts/lint.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Run linting, formatting and type checking
 
 echo "Running Ruff linter..."

.scripts/test.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 # Run tests with coverage
 
 echo "Running tests with coverage..."