fix(browser): send extraction schemas under json_schema - #2034

This PR fixes Browser Run schema extraction by sending schemas under response_format.json_schema and aligning the exported Quick Action type and examples with the service contract. Fixes #2029.

Why

• browser_extract accepts a model-facing schema, but forwarded it to Browser Run as response_format.schema. Browser Run requires response_format.json_schema, so every schema-based extraction failed with HTTP 400.
• The implementation and exported type followed an outdated Browser Run documentation example. The unit test used a fake binding and asserted the same incorrect payload, so it could not detect the contract mismatch.
• This corrects the SDK to use the service-native field rather than supporting two spellings. The old spelling never produced a valid schema-based Browser Run request.

Public API Surface

• QuickActionExtractInput.response_format now uses json_schema instead of schema.
• The model-facing browser_extract input remains unchanged: models still pass the schema through its top-level schema field.

Code Changes

• Map browser_extract schemas to response_format.json_schema.
• Align the Quick Action extraction type with Browser Run and Workers Types.
• Add type coverage that accepts json_schema and rejects the invalid schema property.
• Update the package documentation and browser Quick Actions example to show the valid request shape.
• Add an agents patch changeset.

Compatibility

Direct callers of browserExtract or runQuickAction that construct response_format must rename its nested schema property to json_schema. The previous property matched the published SDK type but was rejected by Browser Run at runtime.