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>

docs/Driver.FOCAS.Cli.md

@@ -5,27 +5,22 @@ protocol. Uses the **same** `FocasDriver` the OtOpcUa server does — PMC R/G/F
 file registers, axis bits, parameters, and macro variables — all through
 `FocasAddressParser` syntax.
 
-Sixth of the driver test-client CLIs, added alongside the Tier-C isolation
-work tracked in task #220.
+Sixth of the driver test-client CLIs.
 
 ## Architecture note
 
-FOCAS is a Tier-C driver: `Fwlib32.dll` is a proprietary 32-bit Fanuc library
-with a documented habit of crashing its hosting process on network errors.
-The target runtime deployment splits the driver into an in-process
-`FocasProxyDriver` (.NET 10 x64) and an out-of-process `Driver.FOCAS.Host`
-(.NET 4.8 x86 Windows service) that owns the DLL — see
-[v2/implementation/focas-isolation-plan.md](v2/implementation/focas-isolation-plan.md)
-and
-[v2/implementation/phase-6-1-resilience-and-observability.md](v2/implementation/phase-6-1-resilience-and-observability.md)
-for topology + supervisor / respawn / back-pressure design.
+FOCAS is an in-process driver. The pure-managed `WireFocasClient`
+speaks the FOCAS2 binary protocol directly over TCP:8193, removing the
+Tier-C process-isolation split that the historical P/Invoke + out-of-
+process Host arrangement required. The CLI loads `FocasDriver` with
+`WireFocasClientFactory` and talks to the CNC without any native
+components.
 
-The CLI skips the proxy and loads `FocasDriver` directly (via
-`FwlibFocasClientFactory`, which P/Invokes `Fwlib32.dll` in the CLI's own
-process). There is **no public simulator** for FOCAS; a meaningful probe
-requires a real CNC + a licensed `Fwlib32.dll` on `PATH` (or next to the
-executable). On a dev box without the DLL, every wire call surfaces as
-`BadCommunicationError` — still useful as a "CLI wire-up is correct" signal.
+A dev-friendly mock is available — start
+`tests/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.IntegrationTests/Docker/docker-compose.yml`
+and point `--cnc-host` at `localhost` for end-to-end CLI exercises
+without a real CNC. See
+[drivers/FOCAS-Test-Fixture.md](drivers/FOCAS-Test-Fixture.md).
 
 ## Build + run
 
@@ -152,7 +147,8 @@ fails.
 **"Why did this macro flip?"** → `subscribe` to the macro, let the
 operator reproduce the cycle, watch the HH:mm:ss.fff timeline.
 
-**"Is the Fwlib32 DLL wired up?"** → `probe` against any host. A
-`DllNotFoundException` surfacing as `BadCommunicationError` with a
-matching `Last error` line means the driver is loading but the DLL is
-missing; anything else means a transport-layer problem.
+**"Can I reach the CNC on TCP:8193?"** → `probe` against any host. A
+`BadCommunicationError` means the wire client couldn't open a socket
+(firewall / wrong host / FOCAS Ethernet option unlicensed on the CNC).
+`BadDeviceFailure` after a successful connect means the CNC is rejecting
+the session setup — check the CNC's FOCAS option and password settings.