docs(windows): align MXC documentation with the implementation #4645

User Story

As the maintainer preparing OpenShell's native Windows MXC relaease we need the Windows documentation to describe the current implementation so users and contributors can follow it without reverse-engineering the code.

Problem Statement

The Windows documentation contains conflicting availability statements, an interactive creation example that does not explicitly detach, obsolete proxy process-identity descriptions, the wrong Windows boundary executable name in RFC 0013, and outdated test and Z3 linkage instructions. The published audit guidance also omits a qualification limitation already documented in the driver README.

Impact / Why This Matters

These discrepancies can lead readers to select an unsupported workflow, omit required runtime files, authorize the wrong executable in network policy, or overestimate audit and isolation coverage. Reading the driver, supervisor, build scripts, and tests is the current workaround; it is insufficient for documentation intended to guide Windows users and contributors.

Description

Reconcile the existing Windows documentation and relevant contributor/public skills with the native MXC implementation. Preserve the experimental support status and documented enforcement limitations. This task changes documentation only.

Context

Related to the native Windows roadmap item #4450. This task covers only the documentation corrections and does not complete the broader Windows roadmap.

The audit uses the windows branch at 624f55b3c6affedd4f2757c7eb32132196b4c3e8 and covers the gateway configuration reference, support/runtime overviews, policy and audit guidance, contributor build instructions, the MXC README, RFC 0013, and the Windows/CLI skills.

Acceptance Criteria

• Availability and runtime guidance describe the experimental native x64/ARM64 MXC path and its supported workflow.
• Creation examples use --detach and an absolute working directory.
• Proxy identity guidance describes the actual socket-owning executable.
• Packaging guidance names the four Windows executables, matching libz3.dll, and runtime prerequisites.
• Contributor instructions match the Windows branch checkout, Nextest tasks, logs, and Z3 import-library linkage.
• Existing outer-fence, loopback, live-revocation, and audit qualification limits remain explicit.
• Documentation, Markdown, diagram, and relevant example/reference checks pass.
• The change contains no runtime code, build-script, or policy-fixture modifications.