feat(spring): @Streaming annotation for binary response streaming

[nsmnds]

Summary

Adds a @Streaming annotation that opts a Bytes response into chunked,
never-fully-buffered response streaming on Spring endpoints — both server
and client (Spring WirespecWebClient) sides.

endpoint DownloadReport GET /api/report -> {
    @Streaming
    200 -> Bytes
}

What changes

• Spring Kotlin/Java emitters substitute org.springframework.core.io.Resource
  for the body type when a response is annotated @Streaming, skip the JSON
  serialize step, and emit a STREAMING marker on the handler companion.
• WirespecResponseBodyAdvice (Kotlin + Java) dispatches on a runtime
  Resource body and writes Resource.inputStream straight to
  response.body with application/octet-stream.
• WirespecWebClient (Kotlin + Java) detects the marker reflectively
  and consumes the response via bodyToMono(Resource.class) instead of
  buffering bytes.
• Validation: @Streaming on a non-Bytes response fails the emit.
• Core emitter hooks: KotlinEndpointDefinitionEmitter and
  JavaEndpointDefinitionEmitter expose three new open hooks
  (emitResponseBodyType, emitResponseSerializeBody,
  emitResponseDeserializeBody) plus a companion-extras hook so per-emitter
  subclasses can override response-body behavior without touching the
  request path.
• concatGenerics sanitizer: now strips dots so fully-qualified body
  types produce valid identifiers.

Out of scope (intentional)

• Other client SDKs (Ktor, OkHttp, JS, Python, etc.) keep buffering via
  the existing RawResponse.body: ByteArray? contract — unchanged.
• fromResponse still works for non-streaming callers (tests, mocks)
  by wrapping the buffered body in ByteArrayResource. The Spring
  streaming client bypasses that path entirely.

Test plan

• :src:compiler:core:jvmTest, :src:compiler:emitters:kotlin:jvmTest,
  :src:compiler:emitters:java:jvmTest — all green
• :src:integration:spring:jvmTest — all green (existing 49 tests +
  6 new emitter tests asserting Resource body / STREAMING marker /
  @Streaming validation for both Kotlin and Java)
• :src:converter:openapi:jvmTest, :src:integration:jackson:jvmTest
  — all green (verifies concatGenerics change is backward-compatible)
• Manual end-to-end: streaming client receives first byte before
  full body for a slow InputStreamResource server (recommended
  follow-up integration test, not yet added)

https://claude.ai/code/session_013z9Zaawbdh3pnyMg4b2DSG

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud