Fix AtlasCloud agent conformance guarded delegation

Root cause: - CI run https://github.com/micro/go-micro/actions/runs/28906255485 failed in the Provider harnesses (live LLM conformance) job on master at 364fb33cc88ea3a5a2a691a6843596af. - The atlascloud / agent harness failed TestAgentProviderConformanceMatrix/atlascloud with: `Ask: provider conformance incomplete after 4 attempts: missing guarded delegate`. - Other configured live providers were skipped because their API keys were absent, so this is isolated to the AtlasCloud live agent conformance path rather than the mock harness. Where: - `go run ./internal/harness/provider-conformance -providers atlascloud -harnesses agent ...` - Package/test reported by the log: `go-micro.dev/v6/agent`, `TestAgentProviderConformanceMatrix/atlascloud`. Acceptance criteria: - AtlasCloud live agent conformance consistently observes the required guarded delegate behavior within the harness retry budget. - The provider-conformance summary reports atlascloud / agent as passed. - The next Harness (E2E) run for Provider harnesses (live LLM conformance) no longer fails with `missing guarded delegate`. Deduplication: - Searched open issues for `missing guarded delegate`, `guarded delegate`, and `atlascloud agent conformance`; no scoped open defect for this exact failure was found.