Fix #7074 report a single field error from aggregate resolver exceptions

[michaelstaib]

Fixes #7074

Summary

• Added a regression test that reproduces throwing an AggregateException with multiple GraphQLException inner exceptions from a single field resolver.
• Updated resolver error reporting in MiddlewareContext to only surface the first field error for GraphQLException and AggregateException containers.
• This aligns field-error behavior with one-error-per-field expectations.

Test Commands

• dotnet test src/HotChocolate/Core/test/Execution.Tests/HotChocolate.Execution.Tests.csproj --filter "FullyQualifiedName~Issue7074ReproTests" --nologo
• dotnet test src/HotChocolate/Core/test/Types.Mutations.Tests/HotChocolate.Types.Mutations.Tests.csproj --filter "FullyQualifiedName~ErrorMiddleware_Should_MapAggregateException_WhenRegistered" --nologo

Results

• Both commands passed on net8.0, net9.0, and net10.0.

[github-actions]

Fusion Gateway Performance Results

Progress: 0/6 benchmarks completed — this report updates as each job finishes.

Simple Composite Query

	Req/s	Err%
Constant 2 (50 VUs)	pending	pending
Ramping 2 (0-500-0 VUs)	pending	pending

Response Times

	Min	Med	Avg	P90	P95	Max
Constant 2	pending	pending	pending	pending	pending	pending
Ramping 2	pending	pending	pending	pending	pending	pending

---

Deep Recursion Query

	Req/s	Err%
Constant 2 (50 VUs)	pending	pending
Ramping 2 (0-500-0 VUs)	pending	pending

Response Times

	Min	Med	Avg	P90	P95	Max
Constant 2	pending	pending	pending	pending	pending	pending
Ramping 2	pending	pending	pending	pending	pending	pending

---

Variable Batching Throughput

	Req/s	Err%
Constant 2 (50 VUs)	pending	pending
Ramping 2 (0-500-0 VUs)	pending	pending

Response Times

	Min	Med	Avg	P90	P95	Max
Constant 2	pending	pending	pending	pending	pending	pending
Ramping 2	pending	pending	pending	pending	pending	pending

---

Runner 2 = benchmarking-2

Run 22499546705 • Commit f3ec2e7 • Fri, 27 Feb 2026 18:54:04 GMT