Docs audit — fill gaps so the top-level docs/ reference matches shipped code

Audit of docs/ against src/ surfaced shipped features without current-reference
coverage (FOCAS CLI, Core.Scripting+VirtualTags, Core.ScriptedAlarms,
Core.AlarmHistorian), an out-of-date driver count + capability matrix, ADR-002's
virtual-tag dispatch not reflected in data-path docs, broken cross-references,
and OpcUaServerReqs declaring OPC-020..022 that were never scoped. This commit
closes all of those so operators + integrators can stay inside docs/ without
falling back to v2/implementation/.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/IncrementalSync.md

@@ -51,6 +51,10 @@ Exceptions during teardown are swallowed per decision #12 — a driver throw mus
 
 When `RediscoveryEventArgs.ScopeHint` is non-null (e.g. a folder path), Core restricts the diff to that subtree. This matters for Galaxy Platform-scoped deployments where a `time_of_last_deploy` advance may only affect one platform's subtree, and for OPC UA Client where an upstream change may be localized. Null scope falls back to a full-tree diff.
 
+## Virtual tags in the rebuild
+
+Per [ADR-002](v2/implementation/adr-002-driver-vs-virtual-dispatch.md), virtual (scripted) tags live in the same address space as driver tags and flow through the same rebuild. `EquipmentNodeWalker` (`src/ZB.MOM.WW.OtOpcUa.Core/OpcUa/EquipmentNodeWalker.cs`) emits virtual-tag children alongside driver-tag children with `DriverAttributeInfo.Source = NodeSourceKind.Virtual`, and `DriverNodeManager` registers each variable's source in `_sourceByFullRef` so the dispatch branches correctly after rebuild. Virtual-tag script changes published from the Admin UI land through the same generation-publish path — the `VirtualTagEngine` recompiles its script bundle when its config row changes and `DriverNodeManager` re-registers any added/removed virtual variables through the standard diff path. Subscription restoration after rebuild runs through each source's `ISubscribable` — either the driver's or `VirtualTagSource` — without special-casing.
+
 ## Active subscriptions survive rebuild
 
 Subscriptions for unchanged references stay live across rebuilds — their ref-count map is not disturbed. Clients monitoring a stable tag never see a data-change gap during a deploy, only clients monitoring a tag that was genuinely removed see the subscription drop.