Make native Windows validation reliable

Tracking issue: MicroVM support and private snapshot restore.

Motivation

A machine profile intended to run on Windows and Linux needs repeatable validation
on both hosts. Native Windows checks must exercise the intended code paths without
depending on an implicit Unix environment or treating unexecuted checks as success.
This provides a useful review baseline for changes to boot, memory, and devices.

Proposed Scope

• Provide native Windows validation for the packages and host-specific paths
  needed by the microVM work.
• Make tool invocation, environment setup, and platform gating explicit.
• Preserve the warning policy and failure propagation used by the corresponding
  build, lint, documentation, and test checks.
• Distinguish hosted checks from tests that require a particular hypervisor or
  privileged runner; report unavailable coverage explicitly.
• Regenerate workflow definitions from Flowey sources when those sources change.

Acceptance Criteria

• The selected checks execute successfully in a native Windows environment
  without requiring WSL.
• A failing build, lint, documentation check, or test produces a failing job
  rather than being lost by a wrapper or shell invocation.
• Logs identify the selected toolchain, validation scope, and any checks that
  could not execute.
• Linux validation retains its coverage and existing machine profiles are not
  excluded to make the Windows job pass.
• Windows setup and validation commands are documented in the relevant
  contributor documentation.

Dependencies

No feature prerequisites. This validation work can be reviewed independently of
the microVM machine profile.

Non-Goals

This issue does not add the machine profile or claim hypervisor coverage from
compile-only or hosted checks.