Resolve Client.Python-001/002/004/006/007/008/010/011/012 findings

Client.Python-001: dropped "scaffold" from the stale pyproject description.
Client.Python-002 (re-triaged): stale finding — MxGatewayCommandError is
already exported and in __all__; no change needed.
Client.Python-004: removed the dead `closed` variable in _smoke; the CLI
smoke now uses `async with session`.
Client.Python-006: close() on both clients and Session had an unlocked
check-then-set race; `_closed` is now set before the await.
Client.Python-007: gateway stream iterators now share one helper that
explicitly catches CancelledError and cancels the call.
Client.Python-008: to_mx_value now rejects nan/inf; float/bytes mapping
documented.
Client.Python-010: removed the circular-import-workaround late imports in
favour of TYPE_CHECKING / module-scope imports.
Client.Python-011: ensure_mxaccess_success no longer treats a proto3-default
success==0 with an unset category as a failure.
Client.Python-012 (Won't Fix): invoke_raw deliberately skips MXAccess-failure
detection for parity tests; documented the contract instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/python/README.md

@@ -95,6 +95,22 @@ async with await GatewayClient.connect(
 events available for parity tests. `Session` helpers call the method-specific
 MXAccess commands and preserve raw replies on typed command exceptions.
 
+`*_raw` methods (`GatewayClient.invoke_raw`, `Session.invoke_raw`) surface
+gateway protocol failures by raising the typed `MxGateway*` exceptions, but
+they deliberately do **not** run MXAccess-failure detection: an MXAccess
+HRESULT or `MxStatusProxy` status failure is left embedded in the returned
+reply and no `MxAccessError` is raised. `Session.invoke` adds that check on
+top. Parity-test callers using `invoke_raw` must inspect the reply's
+`protocol_status`, `hresult`, and `statuses` themselves. The non-raw `Session`
+helpers (`register`, `add_item`, `write`, the bulk methods, etc.) run the
+check and raise `MxAccessError`.
+
+Value conversion (`to_mx_value`, used by `Session.write`/`write2` and the
+bulk helpers) rejects non-finite floats — `nan`, `inf`, and `-inf` raise
+`ValueError` rather than being forwarded to MXAccess, which has no defined
+wire representation for them. Python `bytes` values are an opaque
+`VT_RECORD` pass-through that MXAccess does not interpret.
+
 Canceling a Python task cancels the client-side gRPC call or stream wait. It
 does not abort an in-flight MXAccess COM call inside the worker process.