chore: ignore generated Playwright MCP artifacts from formatting

[ubugeeei]

Finding

Local generated browser artifacts are included in Prettier checks, so a developer can fail npm run format:check without touching product code.

Evidence

• npm run format:check fails on .playwright-mcp/page-*.yml in this checkout.
• .prettierignore and .gitignore do not currently ignore .playwright-mcp.

Acceptance criteria

• Ignore .playwright-mcp in .gitignore and .prettierignore.
• npm run format:check passes with local Playwright MCP artifacts present.

[ubugeeei]

対応済みです。修正は PR #1 / commit 9cf4498 に反映済みです。