Phase 6.2 Stream C.12 — lock in ScopePathIndexBuilder semantics with tests

Closes task #123 (partial — builder semantics unit-tested; production
wiring is the new task #133).

ScopePathIndexBuilder + NodeScopeResolver indexed mode already exist —
they produce a full Cluster → Namespace → UnsArea → UnsLine → Equipment
→ Tag scope from the published generation's config rows. What was
missing: unit coverage of the Build semantics (the only consumers were
compile-time references) + explicit acknowledgement in the readiness
doc that the gate/resolver aren't yet wired into Program.cs.

Tests — 6 cases in ScopePathIndexBuilderTests.cs:
- Well-formed content emits full hierarchy.
- Tags with null EquipmentId skipped (SystemPlatform-namespace fallback).
- Tags with broken Equipment FK skipped (publish-time validation
  should have caught; builder is defensive).
- Equipment with broken Line FK skipped.
- Duplicate TagConfig throws InvalidOperationException.
- Resolver with index returns full-path scope; un-indexed ref falls
  through to cluster-only scope (pre-ADR-001 behaviour preserved).

Server.Tests 277 → 283.

Critical follow-up (task #133): Program.cs still constructs
OpcUaApplicationHost WITHOUT authzGate or scopeResolver, so all six
dispatch-layer gates (Read, Write, HistoryRead, Browse,
CreateMonitoredItems, Call) are currently inert in production. Wiring
them up — load NodeAcl + EquipmentNamespaceContent at bootstrap,
construct gate + resolver, pass into OpcUaApplicationHost, rebind on
generation refresh — is the last Phase 6.2 GA blocker.

Docs: v2-release-readiness.md Phase 6.2 Stream C hardening list marks
the scope-resolution bullet struck-through with a close-out note that
calls out the gate-inert-in-production gap + task #133.

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

docs/v2/v2-release-readiness.md

@@ -38,7 +38,7 @@ Remaining Stream C surfaces (hardening, not release-blocking):
 - ~~CreateMonitoredItems + TransferSubscriptions gating with per-item `(AuthGenerationId, MembershipVersion)` stamp so revoked grants surface `BadUserAccessDenied` within one publish cycle (decision #153).~~ **Partial, 2026-04-24.** `DriverNodeManager.CreateMonitoredItems` override pre-gates each request and pre-populates `BadUserAccessDenied` into the errors slot for denied items (the base stack honours pre-set errors and skips those items). Decision #153's per-item `(AuthGenerationId, MembershipVersion)` stamp for detecting mid-subscription revocation is still to ship — needs subscription-layer plumbing. TransferSubscriptions not yet wired (same pattern).
 - ~~Alarm Acknowledge / Confirm / Shelve gating.~~ **Partial, 2026-04-24.** Acknowledge + Confirm map to dedicated `OpcUaOperation.AlarmAcknowledge` / `AlarmConfirm` via `MapCallOperation`; Shelve falls through to generic `OpcUaOperation.Call` (needs per-instance method NodeId resolution to distinguish — follow-up).
 - ~~Call (method invocation) gating.~~ **Closed 2026-04-24.** `DriverNodeManager.Call` override pre-gates each `CallMethodRequest` via `GateCallMethodRequests`. Denied calls return `BadUserAccessDenied` without running the method. Alarm methods map to alarm-specific operation kinds; everything else gates as generic `Call`.
-- Finer-grained scope resolution — current `NodeScopeResolver` returns a flat cluster-level scope. Joining against the live Configuration DB to populate UnsArea / UnsLine / Equipment path is tracked as Stream C.12.
+- ~~Finer-grained scope resolution — current `NodeScopeResolver` returns a flat cluster-level scope. Joining against the live Configuration DB to populate UnsArea / UnsLine / Equipment path is tracked as Stream C.12.~~ **Partial, 2026-04-24.** `ScopePathIndexBuilder` + indexed-mode `NodeScopeResolver` exist and are unit-tested — index keys driver-side full-ref → full `Cluster → Namespace → UnsArea → UnsLine → Equipment → Tag` scope. **Critical follow-up (task #133):** Program.cs does not yet construct either the gate or the resolver — all six dispatch-layer gates (Read, Write, HistoryRead, Browse, CreateMonitoredItems, Call) are currently inert in production. Wiring is required before GA.
 - 3-user integration matrix covering every operation × allow/deny.
 
 ### ~~Config fallback — Phase 6.1 Stream D wiring~~ (task #136 — **CLOSED** 2026-04-19, PR #96)