feat(models): expose market combo status

[kartojal]

Summary

• add ComboKnownStatus for the documented pending, enabled, and disabled values
• expose the open ComboStatus response type as market.state.combo_status
• pass newly introduced status strings through instead of rejecting the market response
• export both status types through the public Python package
• cover known and unknown response parsing in the Gamma market model tests

Testing

• make check
• 2310 non-integration tests passed

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Note

Low Risk
Additive Gamma model field and type exports only; no trading, auth, or runtime behavior changes.

Overview
Gamma market responses now surface API comboStatus as market.state.combo_status, with public types ComboKnownStatus (pending, enabled, disabled) and ComboStatus (known values plus arbitrary strings for forward compatibility).

Flat payload normalization maps comboStatus into nested market state alongside existing flags. ComboKnownStatus and ComboStatus are re-exported from the top-level package. Unit tests assert parsing for a known status and that unrecognized values are accepted as plain strings instead of failing validation.

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