feat: add new providers and update chat generation schema

[mattapperson]

Summary

This PR updates the OpenAPI specification and TypeScript SDK to support:

• New model providers (Mara, Sourceful, Xiaomi)
• Extended reasoning effort levels (xhigh)
• Enhanced provider routing with throughput and latency constraints
• Plugin improvements (enabled flag for web-search and file-parser)
• Schema refinement for BigNumberUnion

Changes

New Providers

• Added Mara to the list of supported providers
• Added Sourceful to the list of supported providers
• Added Xiaomi to the list of supported providers

Reasoning Effort

• Added xhigh as a new reasoning effort level option

Provider Routing Enhancements

• Added min_throughput parameter: Minimum tokens per second required from providers
• Added max_latency parameter: Maximum allowed latency in seconds for requests

Plugin Improvements

• Added enabled boolean flag to web-search plugin (defaults to true)
• Added enabled boolean flag to file-parser plugin (defaults to true)
• Allows fine-grained control over plugin activation

Schema Improvements

• Simplified BigNumberUnion type to use string format only (previously allowed number or string)

Impact

• 63 files changed with 2,339 insertions and 515 deletions
• Updates OpenAPI spec, generated TypeScript models, and documentation
• Backward compatible - new fields are optional

Generated Changes

This PR includes auto-generated SDK code from Speakeasy based on the updated OpenAPI specification.