fix(ci): restore R10 post-merge release gates

[masarray]

Purpose

CI-only repair after the physically proven R10 baseline merge.

Fixes

• whitelist the first-party R10 post-merge workflow in the clean-room convergence authority list;
• checkout the immutable ARIEC61850 engine as the sibling repository expected by the existing ARSAS project references;
• keep engine pin 648124097621046f5f127ceb1cf853fea54db730 unchanged.

Safety boundary

• no ARSAS runtime/application source changes;
• no MMS/discovery/reporting/SCL/cache/export behavior changes;
• no engine-lock changes;
• PR perf(scl): reuse short-lived save enrichment snapshot #327 remains separate and is not included;
• merge only after exact-head CI is green.

This PR exists only to unblock validation and stable publication of the already physical-proven R10 lineage.

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