fix(encoding): generate transitive MarshalJSON for wrapper messages with int64_encoding=NUMBER nested fields

[hasanMshawrab]

Summary

Fixes a bug where response/wrapper messages containing nested messages with int64_encoding=NUMBER fields had their int64 values serialized as strings instead of JSON numbers.

• marshalResponse checks for json.Marshaler before dispatching — only the inner message had MarshalJSON() generated, not the outer wrapper
• protojson.Marshal (the fallback) uses protobuf reflection and never calls json.Marshaler methods on nested messages
• Both httpgen and clientgen had the identical gap

Root cause

// marshalResponse in *_http_binding.pb.go
if marshaler, ok := response.(json.Marshaler); ok {
    return marshaler.MarshalJSON()  // works for inner message directly
}
return protojson.Marshal(msg)       // called for wrapper — bypasses inner MarshalJSON

collectInt64EncodingMessages only generated MarshalJSON() for messages with direct NUMBER fields. Wrapper messages that merely referenced such types were not detected.

Fix

Two-phase collection in generateInt64EncodingFile:

1. Phase 1 (existing): detect messages with direct NUMBER-encoded int64 fields
2. Phase 2 (new): detect wrapper messages whose fields are of a type from phase 1
3. Generate wrapper MarshalJSON/UnmarshalJSON that use protojson.Marshal for base serialization, then re-marshal each nested field via json.Marshal — triggering the inner message's custom method

Changes

• internal/httpgen/encoding.go — added Int64WrapperContext, collectWrapperContexts, collectWrapperMessages, generateWrapperMarshalJSON, generateWrapperUnmarshalJSON
• internal/clientgen/encoding.go — identical fix
• internal/httpgen/testdata/proto/int64_nested_encoding.proto — new test proto with SensorReading (inner, NUMBER fields) and GetSensorReadingResponse/GetMultiSensorResponse (wrappers)
• internal/clientgen/testdata/proto/int64_nested_encoding.proto — symlink to above
• Golden files updated for both generators

Test plan

• go test -run TestHTTPGenGoldenFiles ./internal/httpgen — PASS (13 cases)
• go test -run TestClientGenGoldenFiles ./internal/clientgen — PASS (14 cases)
• ./scripts/run_tests.sh --fast — all relevant packages PASS
• Golden file int64_nested_encoding_encoding.pb.go contains MarshalJSON/UnmarshalJSON for SensorReading, GetSensorReadingResponse, and GetMultiSensorResponse

Closes #124

🤖 Generated with Claude Code

[github-actions]

🔍 CI Pipeline Status

✅ Lint: success
✅ Test: success
✅ Coverage: success
✅ Build: success
✅ Integration: success

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[codecov]

Codecov Report

❌ Patch coverage is 0% with 218 lines in your changes missing coverage. Please review.
✅ Project coverage is 3.09%. Comparing base (917521f) to head (e8e52a6).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
internal/clientgen/encoding.go	0.00%	109 Missing ⚠️
internal/httpgen/encoding.go	0.00%	109 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##            main    #125      +/-   ##
========================================
- Coverage   3.17%   3.09%   -0.09%     
========================================
  Files         47      47              
  Lines       7485    7701     +216     
========================================
  Hits         238     238              
- Misses      7243    7459     +216     
  Partials       4       4              

Flag	Coverage Δ
unittests	3.09% <0.00%> (-0.09%)	⬇️

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