Update message format to align with OTel spec completely

[nikhilNava]

Updates message format types and wrappers to fully align with the OpenTelemetry specification.

 Before (versioned envelope):
 {
   "version": "0.1.0",
   "messages": [
     {
       "role": "user",
       "parts": [{ "type": "text", "content": "Hello" }]
     }
   ]
 }

After (plain array per OTel spec):

 [
   {
     "role": "user",
     "parts": [{ "type": "text", "content": "Hello" }]
   }
 ]

For output messages, finish_reason is now always present:

 [
   {
     "role": "assistant",
     "parts": [{ "type": "text", "content": "Hi there" }],
     "finish_reason": "stop"
   }
 ]

The outer { "version", "messages" } wrapper is removed — messages serialize directly as an array.

Changes

• Updated \MessageTypes.cs\ to align type naming with OTel spec
• Refactored \MessageWrappers.cs\ for spec compliance
• Updated \MessageUtils.cs\ accordingly
• Updated all related tests to reflect the new format

[github-actions]

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Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

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[Copilot]

Pull request overview

This PR updates the observability “gen_ai.*.messages” serialization and related helpers/tests to align the emitted message payloads more closely with the OpenTelemetry gen-ai semantic conventions (moving to a plain JSON array format and updating message model details).

Changes:

• Changed message wrapper serialization from a versioned object wrapper to a plain JSON array.
• Updated OutputMessage to always provide a finish_reason (defaulting to "stop").
• Refreshed unit/integration tests to assert the new JSON array format.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Observability/Runtime/Tracing/MessageUtils.cs	Updates normalization/serialization docs and changes diagnostic fallback payload format.
src/Observability/Runtime/Tracing/Contracts/Messages/MessageWrappers.cs	Removes versioned wrapper surface and adds JSON converters to serialize wrappers as plain arrays.
src/Observability/Runtime/Tracing/Contracts/Messages/MessageTypes.cs	Makes finish_reason non-null and defaults it to "stop".
src/Tests/Microsoft.Agents.A365.Observability.Runtime.Tests/Tracing/Scopes/OutputScopeTest.cs	Updates assertions to expect JSON arrays for output messages.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.Tests/Tracing/Scopes/InvokeAgentScopeTest.cs	Updates assertions to expect JSON arrays for input/output messages.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.Tests/Tracing/Scopes/InferenceScopeTest.cs	Updates assertions to expect JSON arrays for input/output messages.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.Tests/Tracing/MessageUtilsTest.cs	Updates serialization tests to validate array-root JSON and finish_reason defaults.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.Tests/Etw/EtwLoggingBuilderTests.cs	Updates ETW attribute assertions for array-root message payloads.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.Tests/DTOs/Builders/OutputDataBuilderTests.cs	Updates output message attribute assertions for new format.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.Tests/DTOs/Builders/InvokeAgentDataBuilderTests.cs	Updates input/output message attribute assertions for new format.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.Tests/DTOs/Builders/ExecuteInferenceDataBuilderTests.cs	Updates input/output message attribute assertions for new format.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.Tests/DTOs/Builders/BaseDataBuilderTests.cs	Updates joined message attribute assertions for new format.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.IntegrationTests/Agent365ExporterE2ETests.cs	Updates E2E exporter assertions for input/output message payloads.
src/Tests/Microsoft.Agents.A365.Observability.Runtime.IntegrationTests/Agent365ExporterAsyncE2ETests.cs	Updates async E2E exporter assertions for input/output message payloads.
src/Tests/Microsoft.Agents.A365.Observability.Extensions.IntegrationTests/SemanticKernelSpanProcessorTests.cs	Updates SK span processor integration assertions for array-root messages.
src/Tests/Microsoft.Agents.A365.Observability.Extensions.IntegrationTests/SemanticKernelInvokeAgentPipelineTests.cs	Updates SK invoke-agent pipeline assertions for array-root messages.
src/Tests/Microsoft.Agents.A365.Observability.Extensions.IntegrationTests/AgentFrameworkSpanProcessorTests.cs	Updates Agent Framework processor assertions for array-root messages.
src/Tests/Microsoft.Agents.A365.Observability.Extensions.IntegrationTests/AgentFrameworkInvokeAgentPipelineTests.cs	Updates Agent Framework invoke-agent pipeline assertions for array-root messages.
src/Tests/Microsoft.Agents.A365.Observability.Extension.Tests/SemanticKernelSpanProcessorHelperTests.cs	Updates helper tests to assert JSON array payloads.