test(driver-mxc): add probe-gated real wxc-exec test lane (no mocks)

- tests/wxc_exec_real.rs: ignored-by-default integration tests against a
  real wxc-exec. Six --dry-run contract tests run wherever the binary
  exists (they caught the network.proxy shape mismatch); enforcement
  tests (processcontainer default-deny positive/negative, isolation
  session lifecycle round trip with a deprovision drop-guard) probe the
  backend and SKIP with a recorded reason where it is not live.
- examples/probe-mxc-host.ps1: classifies a host (OS build, --probe,
  per-backend trial) and emits a JSON capability verdict.
- examples/run-mxc-e2e.ps1 + e2e-policies/: scenario runner generalizing
  run-demo.ps1 (fs-rw, fs-readonly, fs-default-deny-empty,
  network-policy-rejected) with PASS/FAIL/SKIP gating and a stale
  OPENSHELL_MXC_MOCK_WXC guard in real mode.
- tasks/windows.toml: windows:test:mxc-real:x64, windows:e2e:mxc,
  windows:e2e:mxc:mock.

Signed-off-by: Giedrius Burachas <gburachas@nvidia.com>
(cherry picked from commit 49afafe892caded59c4df50a9b652011ad97f41c)
Signed-off-by: Jamie King <jamiek@nvidia.com>

crates/openshell-driver-mxc/README.md

@@ -108,6 +108,35 @@ the demo Windows host and follow `mxc-demo-runbook.md` inside it. The
 script prints a SHA256 manifest so the operator can sanity-check what
 landed before moving it.
 
+## Real-MXC test lane
+
+Three tasks drive real `wxc-exec.exe` hardware; all are **skip-safe** — any test
+or scenario that requires an absent binary or backend prints a SKIP reason and
+exits 0 rather than failing.
+
+| Task | What it runs | When to use |
+|---|---|---|
+| `windows:test:mxc-real:x64` | `tests/wxc_exec_real.rs` — Tier-2 invoker tests with `--ignored --test-threads=1` | Pre-merge on any Windows host that has `wxc-exec`; dry-run tests always pass; enforcement tests probe-gate themselves |
+| `windows:e2e:mxc` | `examples/run-mxc-e2e.ps1` — Tier-3 scenario runner, real binary, probe-gated | Demo box / nightly; needs the gateway + CLI binaries in the script directory |
+| `windows:e2e:mxc:mock` | Same runner with `-Mock` — wiring-only, no real `wxc-exec` needed | Any Windows host (CI, dev machine); validates wiring and the network-reject scenario |
+
+**Probe script:** `examples/probe-mxc-host.ps1` emits a JSON capability report
+(OS build, wxc-exec path/version, dry-run exit code, per-backend trial result,
+and a `verdicts` object). Run it before the real-MXC lane to understand what
+will PASS vs SKIP on a given host:
+
+```powershell
+powershell -NoProfile -ExecutionPolicy Bypass `
+  -File crates/openshell-driver-mxc/examples/probe-mxc-host.ps1
+```
+
+**Skip semantics:** tests in `wxc_exec_real.rs` are marked
+`#[ignore = "requires real wxc-exec"]` — the standard `windows:test:x64` suite
+never runs them. `OPENSHELL_WXC_EXEC_PATH` overrides the default
+`C:\mxc\wxc-exec.exe` lookup. See `docs4gtb/mxc-box-capabilities.md` for the
+empirical capability snapshot of the development box (build 26200, processcontainer
+velocity keys not enabled, isolation_session absent).
+
 ## Deferred work
 
 - **Interactive exec/connect/forward** → `adapt-openshell-gateway-windows`

crates/openshell-driver-mxc/examples/e2e-policies/fs-empty.yaml

@@ -0,0 +1,15 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# fs-empty.yaml — Empty filesystem policy (default-deny) scenario.
+#
+# No paths are granted. With processcontainer (AppContainer), every write is
+# denied by the OS without any host ACL configuration — genuine default-deny.
+# This scenario is processcontainer-only (isolation_session has no deny primitive).
+# Used by the fs-default-deny-empty scenario in run-mxc-e2e.ps1.
+version: 1
+
+filesystem_policy:
+  include_workdir: false
+  read_only: []
+  read_write: []

crates/openshell-driver-mxc/examples/e2e-policies/fs-readonly.yaml

@@ -0,0 +1,16 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# fs-readonly.yaml — Read-only grant + read-write share scenario.
+#
+# The read_only path is a prepared directory whose content the agent can read
+# but not write; the read_write path is DemoDir (host-visible share).
+# Used by the fs-readonly scenario in run-mxc-e2e.ps1.
+version: 1
+
+filesystem_policy:
+  include_workdir: false
+  read_only:
+    - "C:/work/openshell-mxc-e2e-ro-src"
+  read_write:
+    - "C:/work/openshell-mxc-e2e"

crates/openshell-driver-mxc/examples/e2e-policies/fs-rw.yaml

@@ -0,0 +1,14 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# fs-rw.yaml — Filesystem read-write grant scenario.
+#
+# Grants read-write access to the DemoDir (substituted at runtime).
+# Used by the fs-rw-positive-negative scenario in run-mxc-e2e.ps1.
+version: 1
+
+filesystem_policy:
+  include_workdir: false
+  read_only: []
+  read_write:
+    - "C:/work/openshell-mxc-e2e"

crates/openshell-driver-mxc/examples/e2e-policies/network-reject.yaml

@@ -0,0 +1,30 @@
+# SPDX-FileCopyrightText: Copyright (c) 2025-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+#
+# network-reject.yaml — Network policy rejection scenario.
+#
+# A filesystem grant plus a network_policies rule. On isolation_session the
+# driver rejects sandbox create at map time with invalid_argument naming the
+# network rule (M1 not yet landed). On processcontainer with egress_proxy
+# disabled, network policy is also rejected.
+#
+# This scenario requires NO live backend — it passes even on this box and in
+# mock mode because the rejection happens in the policy mapper before wxc-exec
+# is invoked. It is the only scenario that never SKIPs.
+version: 1
+
+filesystem_policy:
+  include_workdir: false
+  read_only: []
+  read_write:
+    - "C:/work/openshell-mxc-e2e"
+
+network_policies:
+  test_rule:
+    name: test-network-reject
+    endpoints:
+      - host: api.example.com
+        port: 443
+        protocol: rest
+        enforcement: enforce
+        access: read-only

tasks/windows.toml

@@ -63,3 +63,18 @@ run_windows = "powershell -NoProfile -ExecutionPolicy Bypass -File tasks/scripts
 description = "Run Windows MSVC checks, release builds, x64 tests, and unsupported-driver contract tests"
 run = "echo 'windows:* tasks require a Windows MSVC host' && exit 1"
 run_windows = "powershell -NoProfile -ExecutionPolicy Bypass -File tasks/scripts/windows-msvc.ps1 ci all"
+
+["windows:test:mxc-real:x64"]
+description = "Run real-wxc-exec Tier-2 integration tests (skip-safe: tests print SKIP when binary/backend absent)"
+run = "echo 'windows:* tasks require a Windows MSVC host' && exit 1"
+run_windows = "cargo test -p openshell-driver-mxc --test wxc_exec_real --target x86_64-pc-windows-msvc -- --ignored --test-threads=1"
+
+["windows:e2e:mxc"]
+description = "Run MXC Tier-3 e2e scenario runner against real wxc-exec (probe-gated; skip-safe on hosts without the binary)"
+run = "echo 'windows:* tasks require a Windows MSVC host' && exit 1"
+run_windows = "powershell -NoProfile -ExecutionPolicy Bypass -File crates/openshell-driver-mxc/examples/run-mxc-e2e.ps1"
+
+["windows:e2e:mxc:mock"]
+description = "Run MXC Tier-3 e2e scenario runner in mock/wiring-only mode (no real wxc-exec required)"
+run = "echo 'windows:* tasks require a Windows MSVC host' && exit 1"
+run_windows = "powershell -NoProfile -ExecutionPolicy Bypass -File crates/openshell-driver-mxc/examples/run-mxc-e2e.ps1 -Mock"