apollo_integration_tests: validate cende blob witness fields in the dummy recorder

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PR Summary

Low Risk
Changes are confined to integration-test harness code (dummy HTTP recorder), not production cende or consensus paths.

Overview
Integration tests no longer use a no-op cende recorder: the local dummy recorder now behaves more like production for witness shipping and validation.

Blob validation: Each write_blob request is parsed as JSON and must include recent_state_commitment_infos and initial_reads. Missing fields yield 400 Bad Request so the cende client’s retry path fails fast instead of treating bad blobs as success.

RecorderStats: A shared RecorderStats tracks blobs received, blobs with commitment infos, invalid blobs, and a commitment_infos_height_offset derived from stored witness block numbers. Flow setup exposes this as FlowSequencerSetup::recorder_stats for assertions.

Height offset endpoint: commitment_infos_height_offset starts as null (empty recorder) and advances after valid blobs with non-empty recent_state_commitment_infos, matching the production recorder contract for one-time witness delivery.

Large payloads: Axum’s default 2MB body limit is disabled on the recorder router so blobs with declared classes and execution info are accepted, as before validation was added.

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• apollo_integration_tests: verify Patricia storage proofs of persisted witnesses in flow tests #14905
• apollo_integration_tests: assert witness-carrying cende blobs reach the recorder in flow tests #14918
• apollo_integration_tests: validate cende blob witness fields in the dummy recorder #14904 👈 (View in Graphite)
• apollo_integration_tests: assert witnesses persisted for committed heights in flow tests #14903
• central_systest_blobs: publish a decoded commitment-infos companion beside the blobs #14917
• central_systest_blobs: carry real witness fields in the regression blobs #14910
• central_systest_blobs: generalize the GCS helpers to fetch and upload arbitrary objects #14920
• workspace,ci: remove the os_input feature (make it unconditional) #14902 : 2 other dependent PRs (#14907 , #14909 )
• main

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