Document every supported 2D animation source format

[Swarek]

Goal

Document the accepted 2D animation-source formats with copyable examples.

Acceptance criteria

• Explain sequence, strip, grid-sheet, json-sheet, and unity-sheet actions.
• Document every required and optional key for each format.
• Include one minimal working render.json example.
• Add a glossary for the 50 runtime animation slots.
• Explain the open source-vault, provenance, and checksum layout.
• Verify every command and path against the current pipeline.

No new source asset is required for this issue.