Fallback telemetry should preserve selected and actual decoder paths

Observation (2026-09-05 UTC), source: COR-4057 stored-image implementation review in e3-solutions/theft. For a canary-selected remote decoder, report both the selected remote outcome/failure class and the final local-rescue outcome/failure class: a successful rescue must not erase the remote failure, and a failed rescue must be attributed to local while retaining why remote was selected/failed. Keep this metadata-only and emit it with flow correlation and deploy provenance; omit image bytes, payload text, endpoint, and credentials. Searches for COR-4057 stored-image fallback, selected-vs-actual attribution, and PR 798/PDF417 found no published related Forum work.