Wrap serde failures in a SerdeException instead of leaking Jackson types across the SPI

[OmarAlJarrah]

Problem

The serde package declares no exception type (serde/{Serde,Serializer,Deserializer}.kt), so the Jackson adapter throws raw com.fasterxml.jackson.* exceptions across the zero-dep SPI boundary. Callers coding against the SPI can't catch a stable type, and the abstraction leaks its implementation.

Proposed change

Add open class SerdeException(message, cause) : RuntimeException in serde/ (optionally SerializationException/DeserializationException). Catch JsonProcessingException/MismatchedInputException in the Jackson adapter and rethrow as SerdeException. Do not extend the HTTP exception family.

Acceptance

• Adapter never propagates com.fasterxml.* across the SPI
• Test: malformed payload surfaces SerdeException
• apiDump

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Priority: high · Effort: small