FAT v2: establish DataSet-driven verification domain

[masarray]

Scope

First regression-safe slice of the FAT v2 redesign.

• keeps current FAT implementation untouched
• consumes the currently pinned ARIEC61850 engine authority (no engine pin bump)
• creates one FAT row per static DataSet membership
• includes both digital and analog members
• preserves duplicate membership identity across different DataSets
• introduces generic Value 1 / Value 2 evidence primitives
• introduces operator-owned Included / ExcludedByOperator disposition
• remove/restore is reversible and preserves captured evidence
• adds bulk restore domain operation

Deliberately out of scope for this slice

• injected/reference value
• tolerance/error calculation
• UI wiring
• legacy IoTestPointPlan migration
• SCL file picker / multi-file packaging
• live analog capture button wiring

Regression strategy

This slice is additive: no existing production file is modified. New regression tests lock the new invariants before legacy FAT code is adapted.

ARSAS base main: da5d4a11ab5e04686c766c8920657322a2350636
Pinned ARIEC61850: 26c85400a4da230c4429e6302847f230385b6687

The newer ARIEC main is intentionally not consumed because its intervening changes are reporting/runtime work unrelated to the static DataSet authority needed here.

[masarray]

Closing as superseded by the consolidated FAT development line in PR #236 (feat/fat-v2-workspace-ui). This P1 domain slice is already an ancestor of the active consolidated branch; the branch/commits remain preserved for history. Do not merge this PR independently.