Un-skip lifecycle-poc TestServiceLifecycle_PipelineError (harness work)

The #1659 fix is applied to the lifecycle-poc arch (`funnel/worker.go` `Worker.Ack`/`Nack` suppress the closed-source-stream io.EOF, in PR #2546). But un-skipping `pkg/lifecycle-poc/service_test.go` `TestServiceLifecycle_PipelineError` surfaces an **orthogonal poc mock-harness issue**: with a fatal source error, the mock source's `Teardown` expectation (from `generatorSource`/`SourcePluginWithTeardown`) is unmet because the fatal-read cleanup path doesn't tear the source down. This is a preview-arch test-harness problem, not a #1659 defect.

To close: adjust the poc test harness (make the source Teardown expectation conditional/AnyTimes for the fatal path, or verify whether the poc *should* teardown a fatally-errored source — possible resource-leak question), then un-skip the test. The poc test currently references #1659 in its skip note; update it once un-skipped.

Start with pkg/lifecycle-poc/service_test.go and the skipped TestServiceLifecycle_PipelineError. Read generatorSource and SourcePluginWithTeardown, then trace the fatal source-error cleanup path in the poc harness. Done means resolving the Teardown expectation appropriately, un-skipping the test, and updating its #1659 skip note.

Written by the indexing model from the issue text.