[dotnet-code] Extract run logger error helper

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> The original pull request description is below.

---

## Summary

Extracted the run logger middleware's cancellation/failure branch into an unexported `logRunError` helper. This keeps the Go logging middleware's internal structure closer to .NET's `LoggingAgent`, where canceled and failed invocation paths are separated into dedicated logging helpers, while preserving existing log messages and levels.

## .NET Reference

- `dotnet/src/Microsoft.Agents.AI/LoggingAgent.cs` - separates canceled and failed invocation logging into private helper methods.

## Public API and Behavior

No public Go API changed. No intentional behavior change was made.

## Tests

- `go test ./agent`

## Notes

Rejected candidates:
- `dotnet/src/Microsoft.Agents.AI.Workflows/Edge.cs` / `workflow/edge.go`: an existing `origin/dotnet-code-edge-connection-helper-b84489a37052b0dc` branch appears to cover edge-connection helper cleanup.
- `dotnet/src/Microsoft.Agents.AI.Workflows/Run.cs` / `workflow/inproc/run.go`: the event sink/bookmark structure is already closely aligned, including incremental `NewEvents` behavior.

The requested upstream git fetch was blocked by the environment, so the .NET reference files were read through the configured read-only GitHub MCP bridge instead.

---

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Show patch (47 lines)

```diff
From 3d6c7951f4fd124990562f80e4f76aa38419205b Mon Sep 17 00:00:00 2001
X-GH-AW-Base-Commit: c9acdbc21c5841cccd0b6df5fa1e35e1e2b16022
From: "github-actions[bot]"
Date: Wed, 16 Sep 2026 22:29:45 +0000
Subject: [PATCH] [dotnet-code] Extract run logger error helper

Split the internal run logger error path into a small helper so cancellation and failure logging mirror the separated .NET LoggingAgent paths without changing behavior.\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
agent/logger.go | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/agent/logger.go b/agent/logger.go
index 644e568..00a4895 100644
--- a/agent/logger.go
+++ b/agent/logger.go
@@ -32,11 +32,7 @@ func (l *runLoggerMiddleware) Run(next RunFunc, ctx context.Context, messages []
l.log(ctx, slog.LevelDebug, "run invoked", slogx.SensitiveData("messages", messages), slogx.SensitiveData("opts", opts))
for update, err := range next(ctx, messages, opts...) {
if err != nil {
- if errors.Is(err, context.Canceled) {
- l.log(ctx, slog.LevelDebug, "run canceled", "error", err)
- } else {
- l.log(ctx, slog.LevelError, "run failed", "error", err)
- }
+ l.logRunError(ctx, err)
} else if l.l.SensitiveData {
l.log(ctx, slog.LevelDebug, "run received update", slogx.SensitiveData("update", update))
}
@@ -48,6 +44,14 @@ func (l *runLoggerMiddleware) Run(next RunFunc, ctx context.Context, messages []
}
}

+func (l *runLoggerMiddleware) logRunError(ctx context.Context, err error) {
+ if errors.Is(err, context.Canceled) {
+ l.log(ctx, slog.LevelDebug, "run canceled", "error", err)
+ return
+ }
+ l.log(ctx, slog.LevelError, "run failed", "error", err)
+}
+
func (l *runLoggerMiddleware) log(ctx context.Context, level slog.Level, msg string, args ...any) {
a, ok := AgentFromContext(ctx)
if ok {
--
2.54.0

```

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> Generated by [.NET-to-Go Code Portability Refactoring Agent](https://github.com/microsoft/agent-framework-go/actions/runs/35157680055) · copilot · gpt55 · 79.6 AIC · ⌖ 15.8 AIC · ⊞ 18.4K · [◷](https://github.com/search?q=repo%3Amicrosoft%2Fagent-framework-go+%22gh-aw-workflow-id%3A+dotnet-code-portability-nightly%22&type=pullrequests)

Review agent/logger.go and the existing branch changes first. Run go test ./agent; the work is done when the run logger uses a private error helper, preserves cancellation and failure messages and levels, and changes no public Go API.

Written by the indexing model from the issue text.