Initial version of stealthii

An aiohttp/httpx-shaped async HTTP client backed by a single, persistent,
stealth-patched Chromium instance via Playwright. get/post/put/patch/
delete/head/download use context.request (real Chrome TLS/HTTP2
fingerprint, no tab needed); render()/screenshot()/page() escalate to
full JS-executing page rendering for targets that need a JS challenge
solved. Supports named sessions for cookie persistence/warm-up, and
`async with stealth as page` to claim a tab directly, task-safe for
concurrent use on one shared instance. Context/browser recycling bounds
cookie and on-disk cache growth in a long-lived process.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0116i7dYLNZTXNR7Lqf439bV

.gitignore

@@ -0,0 +1,8 @@
+__pycache__/
+*.pyc
+.venv/
+*.egg-info/
+dist/
+build/
+.pytest_cache/
+.ruff_cache/