ci(consume-test): force fresh download to surface SHA mismatch

[kcenon]

What

Force fresh download in kcenon/vcpkg-registry's vcpkg-consume-test.yml workflow so that SHA mismatches are surfaced instead of silently sidestepped by vcpkg's archive cache.

Part of #674 (kcenon/common_system).

Why

The weekly vcpkg-consume-test.yml PASSED throughout the period when all 8 kcenon ports had SHA mismatches in their portfiles (see #87 for the audit). The reason: vcpkg's archive cache hits sidestep SHA verification on subsequent installs. New cold-cache consumers (new CI runners, new users) hit 100% install failure on every kcenon port — but the consume-test never noticed because the runner kept warming the cache.

This is the primary detection gap: the test infrastructure that should have caught the systemic flaw was masked by the very caching layer it was meant to validate against.

Where

Item	Value
Repository	kcenon/vcpkg-registry
Workflow file	.github/workflows/vcpkg-consume-test.yml
Affected steps	Any step that runs vcpkg install kcenon-*

How

Implementation options (pick one based on workflow shape)

1. Per-job binary cache disable — pass --no-binary-caching to vcpkg install (or set X_VCPKG_NO_BINARY_CACHE=1) so the registry download is forced to re-verify against the portfile SHA every run.
2. Per-job runner cleanup — clean ${VCPKG_DEFAULT_BINARY_CACHE} and the archive cache at the start of each job so subsequent installs cannot rely on a previous run's verified archive.
3. Matrix expansion — add a "cold-cache" matrix dimension that runs at least one job per cycle on a fresh runner with empty caches.

Prefer option 1 if vcpkg supports the flag in the version pinned in the workflow; fall back to option 2 otherwise.

Acceptance criteria

• vcpkg-consume-test.yml runs at least one matrix combination per cycle without binary caching (or with explicitly cleared caches)
• A deliberate SHA mismatch in a port produces a failing CI run (verified by a test PR that intentionally corrupts a SHA, then reverts)
• Workflow YAML documents WHY the no-cache mode exists with a comment pointing back to #674

References

• Parent EPIC: [EPIC] Harden release SHA512 automation across all 8 kcenon systems common_system#674
• First finding: chore(vcpkg): submit kcenon-common-system to microsoft/vcpkg official registry common_system#653 ([kcenon-common-system] new port microsoft/vcpkg#51511)
• Cross-port audit: fix(port): kcenon-common-system portfile SHA512 mismatch (silent until cache miss) #87