Preview draft fighter packs in the Animation Lab

[Swarek]

Problem

Generated fighter packs begin as drafts, but drafts cannot currently be previewed in the Animation Lab. Authors must complete a large contract before seeing their first result.

Desired behavior

Add a targeted draft-preview path such as npm run fighter:preview -- <id> or fighter:build -- <id> --draft.

Acceptance criteria

• A selected draft can appear in the Animation Lab without entering the public character-select roster.
• The Lab displays a visible draft badge and missing-slot checklist.
• Previewing a draft never changes a normal public build or generated release registry.
• Invalid paths and prohibited assets remain rejected.
• Automated tests cover draft selection, roster exclusion, and cleanup.