chore(release): complete Phase 4 rollout-hardening checklist

[joshsadam]

What to build

Turn the existing Phase 4 rollout-hardening scaffold into an executable release gate for Pathogen View Components.

The completed checklist should verify that consumer documentation matches the shipped stylesheet, JavaScript registration, importmap, and demo contracts; consolidate automated and manual validation for high-risk DataGrid and interactive-component behaviour; and detect hidden host Tailwind or legacy integration dependencies before release.

Acceptance criteria

• Consumer-facing setup documentation matches the actual asset and JavaScript registration contracts.
• High-risk keyboard, focus-restoration, screen-reader, fallback, and styling flows have explicit automated or manual verification steps.
• A repository-level check identifies hidden host Tailwind and obsolete integration dependencies.
• The checklist defines clear pass, fail, and deferral evidence for release readiness.
• Existing phase validation documents are reused or linked instead of duplicated.

Blocked by

• Paginated virtual DataGrid work in Add paginated virtual DataGrid rows #62 / Data grid pagy scroll #63 must be stable enough to validate its final consumer contract.