G2.6 P1.6: stabilize multi-RCB dynamic DataSet identity

[masarray]

Goal

Make P1.6 multi-RCB dynamic runtime safe under ARSAS' mandatory per-plan fresh execution revalidation.

The generic hybrid planner numbers temporary DataSets by plan order (AR_HYB_01, AR_HYB_02, ...). During execution ARSAS intentionally revalidates one RCB immediately before each write; an isolated second group would otherwise renumber to _01, potentially colliding with the already-active first DataSet when both RCBs live in the same logical device.

Change

Adds MmsGuardedDynamicReportFieldCapabilityStableRuntimePlanner, a narrow wrapper over PR #104's field-capability planner. It changes only temporary dynamic DataSet identity:

• each exact dynamic RCB gets a deterministic AR_HYB_<SHA256-prefix> name derived from its RCB reference;
• the same RCB keeps the same DataSet reference in full planning and isolated revalidation;
• different RCBs get different names independent of plan order;
• assignments and diagnostic steps are updated consistently.

Non-change

• no change to member scope or grouping;
• no change to fresh RCB availability gates;
• no change to static precedence;
• no change to dynamic plan/member limits;
• no ProductionEligible authorization;
• no profile mutation/save.

Regression

Tests prove full-plan vs isolated-revalidation stability for the same RCB, uniqueness across two RCBs in the same logical device, and that static segments / ProductionEligible boundary remain unchanged.