test(e2e): keep empty-feed failure detection independent of notice wording #383

J-EDGE-05 now requires a real empty-feed request, an empty episode list, the empty-state message, and absence of the exact load-error Notice. A real product mutation fetches the empty response then throws. The new Notice assertion rejects that mutation on today's plugin.

Independent fourth-round review identified a future regression gap. If the v3 rewrite changes the load-error Notice wording, the negative exact-string check can silently stop rejecting a failed empty-feed load. The positive empty-list assertions still pass on that error path.

Make the negative assertion independent of the exact sentence, for example by asserting that no error Notice mentions the fixture podcast. Prove it rejects both the current failure text and a reworded load failure. Retain the empty-channel success checks and real request assertion.

The current product text matches and the mutation proof passes. This is a follow-up under the coordinator's explicit no-fifth-fix-round decision, not an observed acceptance-run defect.