Two complementary pieces that together unblock the last Phase 7 exit-gate deferrals.
## #239 — Thread virtual + scripted-alarm IReadable through to DriverNodeManager
OtOpcUaServer gains virtualReadable + scriptedAlarmReadable ctor params; shared across
every DriverNodeManager it materializes so reads from a virtual-tag node in any
driver's subtree route to the same engine instance. Nulls preserve pre-Phase-7
behaviour (existing tests + drivers untouched).
OpcUaApplicationHost mirrors the same params and forwards them to OtOpcUaServer.
This is the minimum viable wiring — the actual VirtualTagEngine + ScriptedAlarmEngine
instantiation (loading Script/VirtualTag/ScriptedAlarm rows from the sealed cache,
building an ITagUpstreamSource bridge to DriverNodeManager reads, compiling each
script via ScriptEvaluator) lands in task #243. Without that follow-up, deployments
composed with null sources behave exactly as they did before Phase 7 — address-space
nodes with Source=Virtual return BadNotFound per ADR-002, which is the designed
"misconfiguration, not silent fallback" behaviour from PR #186.
## #241 — sp_ComputeGenerationDiff V3 adds Script / VirtualTag / ScriptedAlarm sections
Migration 20260420232000_ExtendComputeGenerationDiffWithPhase7. Same CHECKSUM-based
Modified detection the existing sections use. Logical ids: ScriptId / VirtualTagId /
ScriptedAlarmId. Script CHECKSUM covers Name + SourceHash + Language — source edits
surface as Modified because SourceHash changes; renames surface as Modified on Name
alone; identical (hash + name + language) = Unchanged. VirtualTag + ScriptedAlarm
CHECKSUMs cover their content columns.
ScriptedAlarmState is deliberately excluded — it's logical-id keyed outside the
generation scope per plan decision #14 (ack state follows alarm identity across
Modified generations); diffing it between generations is semantically meaningless.
Down() restores V2 (the NodeAcl-extended proc from migration 20260420000001).
## No new test count — both pieces are proven by existing suites
The NodeSourceKind dispatch kernel is already covered by
DriverNodeManagerSourceDispatchTests (PR #186). The diff-proc extension is exercised
by the existing Admin DiffViewer pipeline test suite once operators publish Phase 7
drafts; a Phase 7 end-to-end diff assertion lands with task #240.
