Add a loop-harness agent example

[PratikDhanave (PratikDhanave)]

Go has full loop-harness support (agent/harness/loop) but examples/ has no sample demonstrating it — the .NET samples include a Harness set (Harness_Step05_Loop), and the parity doc lists "richer sample coverage" as a gap.

Change

• New examples/02-agents/harness/step01_loop that wraps a Foundry agent with the loop middleware + a completion-marker evaluator, so the agent keeps working across turns until it ends a response with the TASK COMPLETE marker.
• Registered in cmd/verifyexamples (env-gated on FOUNDRY_PROJECT_ENDPOINT, FOUNDRY_MODEL optional), matching the sibling agent samples. It skips cleanly when credentials are absent.

Builds, go vet, and gofumpt clean; the verifyexamples test passes and the new entry is discovered and skips without credentials.

[Copilot]

Copilot review overview

🟢 Approval recommended

Only a non-blocking documentation nit remains.

Review effort: Lite
Findings: None

What changed in this PR

Adds a Foundry-backed loop-harness agent example and registers it for environment-gated verification.

Changes:

• Demonstrates completion-marker loop middleware.
• Registers the sample with verifyexamples.

File	Summary
examples/​02-agents/​harness/​step01_loop/​main.go	New Foundry loop-harness sample.
cmd/​verifyexamples/​examples.go	Registers the sample for verification.

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[github-actions]

Scope: examples

Changed Go contract: None (no exported API added/changed). New example examples/02-agents/harness/step01_loop/main.go and a corresponding entry registered in cmd/verifyexamples/examples.go. Both changes use pre-existing public APIs (agent/harness/loop.New, loop.NewCompletionMarkerEvaluator, foundryprovider.NewAgent) without modification.

Upstream evidence reviewed: dotnet/samples/02-agents/Harness/Harness_Step05_Loop/Program.cs (Harness_Step05_Loop sample) — specifically its Pattern 1 "Completion-marker (Ralph-style) loop" using LoopAgent + CompletionMarkerLoopEvaluator. The Go example's loop.New + loop.NewCompletionMarkerEvaluator(loop.CompletionMarkerConfig{Marker: completionMarker}) wrapping a Foundry-backed agent is a direct conceptual match for this pattern (re-invoke the agent until it emits a completion marker in its response). No Python samples/ equivalent was found for the Harness/loop scenario; Go and .NET currently lead on this sample area, which is consistent with the PR's stated goal of closing a documented Go sample-coverage gap.

Result: aligned. This PR only adds a new example and registers it in the example-verification harness; it introduces no new or changed exported Go API and no behavior change to agent/harness/loop. The example correctly demonstrates the existing loop-harness middleware and mirrors the completion-marker pattern from the upstream .NET Harness_Step05_Loop sample (one of its four patterns — the other three, e.g. todo-based and AI-judge loops, are not covered here but that's an acceptable, non-blocking scope choice for an initial sample). No parity issues found.

Generated by Go API Consistency Review Agent · copilot · auto · 28.7 AIC · ⌖ 6.85 AIC · ⊞ 9.2K · ◷