FOCAS — retire Tier-C split, inline managed wire client, make read-only

Migration closes the FOCAS Tier-C architecture. OtOpcUa previously had
`Driver.FOCAS.Host` (NSSM-wrapped Windows service loading Fwlib64.dll via
P/Invoke) + `Driver.FOCAS.Shared` (MessagePack IPC contracts) + a C shim
DLL stand-in for unit tests. All of it is deleted; the driver is now a
single in-process managed assembly talking the FOCAS/2 Ethernet binary
protocol directly on TCP:8193.

Architecture

- Pure-managed `FocasWireClient` inlined at `src/.../Driver.FOCAS/Wire/`
  (owner-imported — see Wire/FocasWireClient.cs for the full surface).
  Opens two TCP sockets, runs the initiate handshake, serialises requests
  on socket 2 through a semaphore, closes cleanly with PDU + socket
  teardown. Both sync `IDisposable` and async `IAsyncDisposable`.
- `WireFocasClient` (same folder) adapts the wire client to OtOpcUa's
  `IFocasClient` surface — fixed-tree reads, PARAM/MACRO/PMC addresses,
  alarms. Writes return `BadNotWritable` by design — OtOpcUa is read-only
  against FOCAS.
- `FocasDriverFactoryExtensions` now accepts `"Backend": "wire"` (default)
  and `"Backend": "unimplemented"`. Legacy `ipc` and `fwlib` backends are
  rejected at startup with a diagnostic pointing at the migration doc.

Deletions

- `src/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Host/` — whole project + Ipc/,
  Backend/, Stability/, Program.cs.
- `src/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Shared/` — Contracts/, FrameReader,
  FrameWriter, whole project.
- `tests/...Driver.FOCAS.Host.Tests/` + `.Shared.Tests/` — whole projects.
- `src/.../Driver.FOCAS/FwlibNative.cs` + `FwlibFocasClient.cs` — 21
  P/Invokes + 7 `Pack=1` marshalling structs + the Fwlib-backed
  `IFocasClient` implementation.
- `src/.../Driver.FOCAS/Ipc/` + `Supervisor/` — IPC client wrapper +
  Host-process supervisor (backoff, circuit breaker, heartbeat, post-
  mortem reader, process launcher).
- `scripts/install/Install-FocasHost.ps1` — NSSM service installer.
- `tests/.../Driver.FOCAS.Tests/{IpcFocasClientTests, IpcLoopback,
  FwlibNativeHelperTests, PostMortemReaderCompatibilityTests,
  SupervisorTests, FocasDriverFactoryExtensionsTests}.cs` — tests that
  exercised the retired surfaces.
- `tests/.../Driver.FOCAS.IntegrationTests/Shim/` — the zig-built C shim
  DLL that masqueraded as Fwlib64.dll.

Solution changes

- `ZB.MOM.WW.OtOpcUa.slnx` drops the 4 retired project refs.
- `src/.../Driver.FOCAS.csproj` drops the Shared ProjectReference, adds
  `Microsoft.Extensions.Logging.Abstractions` for the optional `ILogger`
  hook in `FocasWireClient`.
- `src/.../Driver.FOCAS.Cli.csproj` drops the six `<Content Include>`
  entries that copied `vendor/fanuc/*.dll` into the CLI bin. CLI now uses
  `WireFocasClient` directly.
- `FocasDriver` default factory flips to `Wire.WireFocasClientFactory`.

Integration tests

- New `tests/.../Driver.FOCAS.IntegrationTests/` project covering fixed-
  tree reads (identity, axes, dynamic, program, operation mode, timers,
  spindle load + max RPM, servo meters), user-authored PARAM / MACRO /
  PMC reads, `DiscoverAsync` emission, `SubscribeAsync` + `OnDataChange`,
  `IAlarmSource` raise/clear transitions, and `ProbeAsync` /
  `OnHostStatusChanged`. 9 e2e tests against the focas-mock fixture
  (Docker container with the vendored Python mock's native FOCAS/2
  Ethernet responder).
- `scripts/integration/run-focas.ps1` orchestrates compose up → tests →
  compose down. Dropped the shim-build stage + DLL-copy step + the split
  testhost workaround (the latter only existed because of native-DLL
  lifecycle bugs the shim tripped).
- Docker compose collapses from 11 per-series services to one `focas-sim`
  service. Tests seed per-series state via `mock_load_profile` at test
  start.
- Vendored focas-mock snapshot refreshed to pick up upstream's native
  FOCAS/2 Ethernet responder (was 660 lines, now 1018) — the
  pre-refresh snapshot only spoke the JSON admin protocol.

Tests

- 145/145 unit tests in `Driver.FOCAS.Tests` pass (was 208 pre-deletion;
  63 removed tests exercised the retired IPC/shim/supervisor/Fwlib
  surfaces).
- 9/9 integration tests pass against the refreshed mock.
- `FocasScaffoldingTests.Unimplemented_factory_throws_on_Create…` updated
  to assert the new diagnostic message pointing at
  `docs/drivers/FOCAS.md` rather than the now-gone `Fwlib64.dll`.

Docs

- `docs/drivers/FOCAS.md` rewritten for the managed wire topology —
  deployment collapses to one `"Backend": "wire"` config block, no
  separate service, no DLL deployment, no pipe ACL.
- `docs/drivers/FOCAS-Test-Fixture.md` updated — single TCP probe skip
  gate instead of TCP + shim probe; fewer moving parts.
- `docs/drivers/README.md` row for FOCAS reflects the Tier-A managed
  topology (previously listed Tier-C + `Fwlib64.dll` P/Invoke).
- `docs/Driver.FOCAS.Cli.md` drops the Tier-C architecture-note section.
- `docs/v2/implementation/focas-isolation-plan.md` marked historical —
  the plan it documents was executed then superseded by the wire client.
- `docs/v2/v2-release-readiness.md` re-audited 2026-04-24. Phase 5
  driver complement closed. FOCAS change-log entry added.

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

scripts/install/Install-FocasHost.ps1

@@ -1,108 +0,0 @@
-<#
-.SYNOPSIS
-    Registers the OtOpcUaFocasHost Windows service. Optional companion to
-    Install-Services.ps1 — only run this on nodes where FOCAS driver instances will run
-    with Tier-C process isolation enabled.
-
-.DESCRIPTION
-    FOCAS PR #220 / Tier-C isolation plan. Wraps OtOpcUa.Driver.FOCAS.Host.exe (net48 x86)
-    as a Windows service using NSSM, running under the same service account as the main
-    OtOpcUa service so the named-pipe ACL works. Passes the per-process shared secret via
-    environment variable at service-start time so it never hits disk.
-
-.PARAMETER InstallRoot
-    Where the FOCAS Host binaries live (typically
-    C:\Program Files\OtOpcUa\Driver.FOCAS.Host).
-
-.PARAMETER ServiceAccount
-    Service account SID or DOMAIN\name. Must match the main OtOpcUa server account so the
-    PipeAcl match succeeds.
-
-.PARAMETER FocasSharedSecret
-    Per-process secret passed via env var. Generated freshly per install if not supplied.
-
-.PARAMETER FocasBackend
-    Backend selector for the Host process. One of:
-      fwlib32      (default — real Fanuc Fwlib32.dll integration; requires licensed DLL on PATH)
-      fake         (in-memory; smoke-test mode)
-      unconfigured (safe default returning structured errors; use until hardware is wired)
-
-.PARAMETER FocasPipeName
-    Pipe name the Host listens on. Default: OtOpcUaFocas.
-
-.EXAMPLE
-    .\Install-FocasHost.ps1 -InstallRoot 'C:\Program Files\OtOpcUa\Driver.FOCAS.Host' `
-        -ServiceAccount 'OTOPCUA\svc-otopcua' -FocasBackend fwlib32
-#>
-[CmdletBinding()]
-param(
-    [Parameter(Mandatory)] [string]$InstallRoot,
-    [Parameter(Mandatory)] [string]$ServiceAccount,
-    [string]$FocasSharedSecret,
-    [ValidateSet('fwlib32','fake','unconfigured')] [string]$FocasBackend = 'unconfigured',
-    [string]$FocasPipeName = 'OtOpcUaFocas',
-    [string]$ServiceName = 'OtOpcUaFocasHost',
-    [string]$NssmPath = 'C:\Program Files\nssm\nssm.exe'
-)
-
-$ErrorActionPreference = 'Stop'
-
-function Resolve-Sid {
-    param([string]$Account)
-    if ($Account -match '^S-\d-\d+') { return $Account }
-    try {
-        $nt = New-Object System.Security.Principal.NTAccount($Account)
-        return $nt.Translate([System.Security.Principal.SecurityIdentifier]).Value
-    } catch {
-        throw "Could not resolve '$Account' to a SID. Pass an explicit SID or check the account name."
-    }
-}
-
-if (-not (Test-Path $NssmPath)) {
-    throw "nssm.exe not found at '$NssmPath'. Install NSSM or pass -NssmPath."
-}
-
-$hostExe = Join-Path $InstallRoot 'OtOpcUa.Driver.FOCAS.Host.exe'
-if (-not (Test-Path $hostExe)) {
-    throw "FOCAS Host binary not found at '$hostExe'. Publish the Driver.FOCAS.Host project first."
-}
-
-if (-not $FocasSharedSecret) {
-    $FocasSharedSecret = [System.Guid]::NewGuid().ToString('N')
-    Write-Host "Generated FocasSharedSecret — store it alongside the OtOpcUa service config."
-}
-
-$allowedSid = Resolve-Sid $ServiceAccount
-
-# Idempotent install — remove + re-create if present.
-$existing = Get-Service -Name $ServiceName -ErrorAction SilentlyContinue
-if ($existing) {
-    Write-Host "Removing existing '$ServiceName' service..."
-    & $NssmPath stop $ServiceName confirm | Out-Null
-    & $NssmPath remove $ServiceName confirm | Out-Null
-}
-
-& $NssmPath install $ServiceName $hostExe | Out-Null
-& $NssmPath set $ServiceName DisplayName 'OT-OPC-UA FOCAS Host (Tier-C isolated Fwlib32)' | Out-Null
-& $NssmPath set $ServiceName Description 'Out-of-process Fwlib32.dll host for OtOpcUa FOCAS driver. Crash-isolated from the main OPC UA server.' | Out-Null
-& $NssmPath set $ServiceName ObjectName  $ServiceAccount | Out-Null
-& $NssmPath set $ServiceName Start SERVICE_AUTO_START | Out-Null
-& $NssmPath set $ServiceName AppStdout (Join-Path $env:ProgramData 'OtOpcUa\focas-host-stdout.log') | Out-Null
-& $NssmPath set $ServiceName AppStderr (Join-Path $env:ProgramData 'OtOpcUa\focas-host-stderr.log') | Out-Null
-& $NssmPath set $ServiceName AppRotateFiles 1 | Out-Null
-& $NssmPath set $ServiceName AppRotateBytes 10485760 | Out-Null
-
-& $NssmPath set $ServiceName AppEnvironmentExtra `
-    "OTOPCUA_FOCAS_PIPE=$FocasPipeName" `
-    "OTOPCUA_ALLOWED_SID=$allowedSid" `
-    "OTOPCUA_FOCAS_SECRET=$FocasSharedSecret" `
-    "OTOPCUA_FOCAS_BACKEND=$FocasBackend" | Out-Null
-
-& $NssmPath set $ServiceName DependOnService OtOpcUa | Out-Null
-
-Write-Host "Installed '$ServiceName' under '$ServiceAccount' (SID=$allowedSid)."
-Write-Host "Pipe: \\.\pipe\$FocasPipeName    Backend: $FocasBackend"
-Write-Host "Start the service with: Start-Service $ServiceName"
-Write-Host ""
-Write-Host "NOTE: the Fwlib32 backend requires the licensed Fwlib32.dll on PATH"
-Write-Host "alongside the Host exe. See docs/v2/focas-deployment.md."