[mathisarends]

CDP values such as CallArgument(value=None) currently become JavaScript undefined, command deadlines exclude sending and custom transports, and the default WebSocket path adds avoidable compression and UTF-8 work. This change fixes those semantics and finalizes the generated API while keeping its scope to typed CDP commands, models, events and transport.

Changes:

• Distinguish omitted optional Any values with UNSET, preserve explicit JSON null, and raise structured CDPDecodeError for missing required fields. Explicit strict=False decoding remains available.
• Enforce one client-owned deadline across sending and receiving for root/session/custom-transport calls. Generated methods retain only CDP parameters; callers use asyncio.timeout() for individual budgets.
• Disable WebSocket compression by default, expose connection options, and send orjson bytes as text frames while receiving bytes directly.
• Generate wire dictionaries directly without intermediate Params instances; retain public Params models and keyword-only signatures.
• Make bounded-stream overflow explicit with overflow="error", retain opt-in drop_oldest, and add root/session/global raw event subscriptions.
• Preserve spec parameter/attribute documentation and experimental/deprecated markers in generated code.
• Add reproducible benchmarks, offline regeneration/drift checking, public API type assertions, and a headless Chrome CI job.

Breaking changes and migration examples are documented in CHANGELOG.md and README.md: optional Any defaults, strict required-field decoding, timeout ownership and None semantics, standalone transport timeout configuration, compression defaults, and bounded-buffer overflow behavior.

The bundled specs are unchanged. Most of the generated diff is attribute/method documentation and direct parameter serialization. The implementation is split into seven commits.

Validation on Windows:

• 298 unit tests passed on Python 3.12, 3.13 and 3.14.
• 7 integration tests passed against real headless Chrome, covering null/undefined, event registration and routing, cancellation cleanup and connection reuse, both JSON backends, compression, and large Unicode payloads.
• Pyright: zero errors or warnings for the complete library and the public API sample.
• Ruff lint/format, bundled-spec generated-code drift check, benchmark smoke run, and wheel build passed.

Reproduce:

uv sync --all-extras --locked
uv run --all-extras pytest
uv run --all-extras pytest -m integration
uv run pyright
uv run python scripts/check_generated.py
uv run python benchmarks/runtime.py