Add TypeScript SDK coordinator schema-mapping tests

[guan404ming]

Related Issue

closes: #69289

Why

Serialization tests validating that camelCase public options map to the supervisor schema's snake_case fields were deferred in #67908.

How

• Add test asserting getXCom defaults locator fields from ctx with snake_case wire names
• Add test asserting absent optional connection wire fields coerce to null public fields
• Extend the dispatch integration test to cover try_number/map_index → tryNumber/mapIndex

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  Claude Code with Fable 5

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