FAT v2 P2: preserve selection and enable rolling evidence capture

[masarray]

Stacked on proven FAT v2 P1

Base branch: feat/fat-dataset-verification-v1
Base SHA: 8493001322b0173f7b75b1b4b83db0d93884edcf
P2 proven head: e5c081c5eb494d43b7d26623b9c528dab20ff219

ARIEC61850 remains pinned to the already-proven engine revision 26c85400a4da230c4429e6302847f230385b6687. P2 does not expand the engine/reporting regression surface.

P2 contract

P2a — operator selection authority

• restore completed/review/failed evidence without auto-unchecking rows
• .arsas package open never excludes completed rows by mutating TestEnabled
• clean retest clears evidence/runtime but preserves operator selection
• persisted TestEnabled is restored exactly as saved

P2b — explicit acquisition scope

• continuation/start no longer temporarily toggles TestEnabled
• preflight validates the real operator selection
• one explicit capture scope is carried through live preparation and Session.Start
• an unchecked/non-ready/out-of-IED point is rejected rather than silently overridden

P2c — rolling evidence capture

• existing current evidence is preserved while a newer candidate cycle is incomplete
• candidate OFF -> ON -> OFF capture runs through the existing transition evaluator on an isolated shadow point
• a complete newer cycle atomically replaces the current ON/OFF pair
• interrupted or rejected recapture leaves the prior current result intact and re-arms capture
• repeated cycles remain possible in one session
• append-only evidence journal retains every accepted/rejected cycle even when current project evidence advances
• reaching a complete current result updates progress/status only; the session remains running until operator Stop
• Stop seals and verifies the evidence journal

Regression evidence

Exact head e5c081c5eb494d43b7d26623b9c528dab20ff219:

• Validate IO List Testing #452 — SUCCESS
• Validate SV evidence bundles #621 — SUCCESS
• Build ARSAS #1509 — SUCCESS
  • source/license boundaries — SUCCESS
  • premium UX / GOOSE / SMV / SAS invariants — SUCCESS
  • immutable ARIEC API verification — SUCCESS
  • solution build — SUCCESS
  • full ARSAS regression suite — SUCCESS
  • portable single-EXE publish — SUCCESS
  • portable EXE smoke test — SUCCESS

The branch is intentionally left unmerged and this PR remains draft for stacked-phase review.

[masarray]

Closing as superseded by consolidated FAT PR #236. This P2 selection/rolling-capture slice is already contained in the active FAT branch ancestry; keeping it open separately now only duplicates review state.