feat!: rebuild Python client for full parity

[smiggleworth]

Summary

• replace the compatibility-oriented API with a typed, asyncio-native clean-break surface
• add bounded request, handler, and subscription runtimes with reconnect restoration and stale-handle safety
• bring KV, Queue, RPC, Lease, Notice, Stream, and Schedule up to the current cross-client wire contract
• own the broker Compose stack and canonical 17-scenario TCP/WebSocket + anonymous/JWT conformance matrix
• add Python-native codec benchmarks, typed wheel metadata, and complete usage/design documentation

Breaking changes

• domain clients are cached properties (client.kv, client.queue, and so on)
• subscriptions are bounded async iterators
• time values use seconds and keyword arguments
• Go-style error aliases and callback compatibility surfaces are removed
• schedule create requires a delivery mode contract and list returns total-count pagination

Local verification

• ruff format --check .
• ruff check .
• pyright src
• pytest tests/unit -q (13 passed)
• wheel and sdist build, including py.typed
• pyperf hot paths: buffer encode/decode and frame parse

Docker is unavailable on the development host, so the repository-owned hosted broker matrix is the authoritative TCP/WebSocket and anonymous/JWT closure gate.

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