PSRP: GET_COMMAND_METADATA support

[irvingoujAtDevolution]

Gap

GET_COMMAND_METADATA is not implemented (message-type ID only). This message powers Get-Command metadata retrieval and implicit remoting (proxy-function generation). Both pypsrp/psrpcore and native C# implement it.

Note: our interactive tab-completion works via a different path (running a command), so this is additive, not a regression.

Current state

• Enum ID only: crates/ironposh-psrp/src/cores.rs (~lines 47, 83). No request builder, no response parsing.

Required

• Build the GET_COMMAND_METADATA pipeline message (command name patterns, command types, module names, ArgumentList).
• Parse the streamed response: CommandMetadataCount, CommandMetadata, ParameterMetadata objects.
• Expose a client-core API (e.g. get_command_metadata(...)).

Acceptance

• An e2e test retrieving metadata for a known cmdlet (e.g. Get-Process) and asserting parameter metadata is parsed.

References

• psrpcore src/psrpcore/_pipeline.py (GetMetadata) + _client.py ClientGetCommandMetadata.
• pypsrp powershell.py get_command_metadata.
• Native C# EncodeAndDecode.cs GenerateGetCommandMetadata (~line 787).