Add CDP session support

[techulus-agent]

Basecamp To-Do: https://app.basecamp.com/5890597/buckets/40504560/todos/10004635981

Summary:

• Add cdp to CreateSessionOptions with skip-if-none serialization.
• Document connectUrl usage and add a CDP session example.
• Keep empty options omitted for existing non-CDP calls.

Verification:

• cargo fmt --check
• CARGO_RESOLVER_INCOMPATIBLE_RUST_VERSIONS=fallback cargo test --all-targets