[masarray]

User acceptance: COMTRADE files named identically belong to one download

Supersedes blocked experimental consumer #600, whose engine pin replacement tripped physically anchored safety/interop CI guards. This safer branch is stacked on green #599, keeps exactly the validated ARIEC pin 036e2c00d83a0815b6160147b14ea05975057965, and does not bypass any engine guard.

• The engine remains the sole authority for complete primary CFG+DAT records and the existing dedicated MMS downloader remains the sole wire/transfer implementation.
• Reconcile only a physically listed .rio file from the same root MMS FileDirectory response with an already verified complete ARIEC CFG/DAT record and exactly matching directory and basename (ordinal). Reject alias duplicates, same-named other-folder files, or missing/mismatched server filename. No SCL or guessed paths.
• Project one verified bundle row line_1, with per-selection members CFG + DAT + RIO and exact count/bytes; orphan RIO remains browse-only.
• Use the engine's existing single transactional downloader by appending the physically observed RIO as an ancillary typed file record. This pinned engine predates a dedicated RIO enum, so its Information kind is used strictly for transfer ordering; extension remains .rio and is never misrepresented as .inf. Future upstream ARIEC #170 can replace this compatibility seam after qualification.
• Existing completed-download validation and hash-based manifest require the extra file. Unknown RIO modification time disables unsafe cached-reuse: no assumption of unchanged remote content.
• Index exact path identities once (O(N) catalog reconciliation), no background network poll, no extra download association, no writes.
• Regression: 3-file logical bundle, physical-only root-first, orphan, duplicate names/case, different directory, incomplete CFG/RIO, missing local RIO / length, source catalog unchanged, SCL-only cannot authorize.

Coverage limitation: root FileDirectory RIO only; the historical engine does not reveal raw unknown extension entries from recursive subdirectory scans. Do not claim subdirectory RIO support without a new engine contract. No main merge or release until CI and BCUGE physical acceptance.

[masarray]

Disposition: Integrated / superseded intermediate M2.14 COMTRADE-RIO compatibility milestone. This is PR tracking cleanup only; no merge to main or physical acceptance.

Canonical replacement: #649 remains OPEN as a preserved integrated application lineage (head 4c232184f64584308396ea18ff6c82700ac02d29). This PR head 1a8601071fc99a5f51719092598b2dd9a94c2a7a is an exact ancestor (GitHub compare ahead=482, behind=0). Current #729/#727 RC contains the production implementation and subsequent engine-compatibility test adaptation.

Unique delta — fully accounted for: All five changed files remain byte-identical in #649 (Git blob SHA verified individually): MainWindow.IedBrowser.Files.cs (d207f127...), Models/IedBrowserFileCatalog.cs (6fa4ffbd...), Models/IedBrowserFileDiscoveryPlanner.cs (85e46d4b...), Models/IedBrowserRioSidecarBridge.cs (aca4a54f...), and tests/ARSAS.Tests/M214RioPinnedEngineCompatibilityTests.cs (283615ca...). In the later RC, all four production files remain exact, while the same six RIO regression test methods were retained and adapted to newer ARIEC engine native RIO support (original expected 2-file CFG/DAT engine catalog upgraded to 3-file CFG/DAT/RIO, plus an explicit idempotence assertion). No orphaned production code/test milestone.

Safety: Original root FileDirectory authority, CFG/DAT/RIO exact-name/path matching, fail-closed ambiguous/orphan RIO, SHA-fenced transfer cache and no fabricated directory scans remain mandatory. No branches deleted and no mutation of ARIEC engine pins, main, stable v1.6.42 or CI/physical gates.

Follow-up: #649 and RC qualification must still verify BCUGE/real-device FileDirectory, native download, COMTRADE bundle behavior and physical FAT before an R7/R10 mainline/source promotion. Closing this historical PR is not acceptance of subdirectory RIO or untested hardware.