Run the full Windows case suites with explicit native MSVC output targets

Part of #611. Difficulty: **medium**. Audit baseline: master `3950416e` (2026-09-12).

## Current evidence

[tests/cases/cases.toml](https://github.com/wavefnd/Wave/blob/3950416efc55cbc5ae7d54535e5a4e8699394ff0/tests/cases/cases.toml#L103) selects Windows OS/architecture without an explicit MSVC target. [.github/workflows/cases.yml](https://github.com/wavefnd/Wave/blob/3950416efc55cbc5ae7d54535e5a4e8699394ff0/.github/workflows/cases.yml#L174) builds amd64 through GNU; ARM64 also provisions llvm-mingw. Existing MSVC object and executor probes do not replace the full case suites.

## Scope

Add native x64/ARM64 MSVC case execution with explicit compiler paths and output triples. Reuse shared, shared/, and windows/ suites; do not clone them just to distinguish GNU from MSVC. Keep compiler-host and generated-target identity visible, and pass the manifest target through matrix generation and runner invocation.

## Completion criteria

Required jobs compile and execute all applicable suites as MSVC programs, keep exact exit/output checks, and publish target-identified reports. Every required tool failure is a failure, not a pass/skip. Preserve case content and coverage; fix actual compiler/provider defects in their focused issues. Existing report/precheck bugs #610, #576 and #577 retain their own ownership. GNU jobs may coexist until the final cutover.

## Dependencies and boundaries

#499 compiler discovery; #612, #613, #617; #608/#609 ARM64 blockers. #462 owns general report identity changes.

Start with tests/cases/cases.toml and .github/workflows/cases.yml at the cited baseline; trace how Windows suites, compiler paths, targets, and matrix entries reach the runner. Run the existing Windows case workflow or its relevant jobs first. Done means native x64 and ARM64 MSVC jobs execute all applicable shared and Windows suites, fail on tool errors, and publish target-identified reports without changing case content.

Written by the indexing model from the issue text.