chore(gitignore): exclude Playwright MCP console-log artifacts

``.playwright-mcp/`` gets auto-created as a scratch directory whenever
the Playwright MCP tool (``mcp__playwright__browser_evaluate`` etc.)
runs against the local docs server for empirical verification. Nothing
in that tree is meant to live in the repo — each entry is a timestamped
console log or snapshot stub that evolves per test run — so ignore it
wholesale.

Author: tony

.gitignore

@@ -205,3 +205,7 @@ cython_debug/
 marimo/_static/
 marimo/_lsp/
 __marimo__/
+
+# Playwright MCP test artifacts (console logs / snapshots written by
+# mcp__playwright when empirically verifying docs behavior)
+.playwright-mcp/