feat(session): add enable_web_bot_auth flag

[devin-ai-integration]

Summary

Adds enable_web_bot_auth to CreateSessionParams (with serialization_alias="enableWebBotAuth") and SessionLaunchState (with alias="enableWebBotAuth") in hyperbrowser/models/session.py. The field is a passthrough to the existing POST /api/session endpoint — no changes to client/managers/{sync,async}_manager/session.py are needed since they post the model dict directly.

When set to True, the server signs every outbound HTTP request from the browser session using Hyperbrowser's Cloudflare-verified bot identity per draft-meunier-web-bot-auth-architecture-02 and RFC 9421. Mutually exclusive with use_stealth and use_ultra_stealth.

This PR is the SDK-surface part of the rollout. Companion PRs:

• hyperbrowserai/node-sdk add gpt-5.5 #76 — enableWebBotAuth field
• hyperbrowserai/docs — sessions/web-bot-auth.mdx, OpenAPI schema, parameters reference
• hyperbrowserai/marketing-site — /.well-known/http-message-signatures-directory JWKS endpoint, blog post, changelog entry

The actual request signing + key management lives in metlo-labs/browserctrl (out of scope for this PR).

Review & Testing Checklist for Human

• Confirm the snake_case → camelCase mapping (enable_web_bot_auth ↔ enableWebBotAuth) matches the wire contract.
• Confirm SDK ships before, after, or alongside the server-side signing work in browserctrl.

Notes

poetry run ruff check hyperbrowser/models/session.py and poetry run ruff format hyperbrowser/models/session.py both pass on the new code. The repo has pre-existing ruff errors elsewhere that this PR does not touch.

Link to Devin session: https://app.devin.ai/sessions/10a58e30bd3e4ec58906f25eab6762a5
Requested by: @shrisukhani

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✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.