Paper canvas rules

Every paper-ds-* skill loads this first.

Before the first write

1. Call get_basic_info with the target fileId. Every file-scoped response carries file.id. If it is not the file you meant, stop and correct fileId. A write to the wrong file cannot be undone.
2. Read paper-ds.json and ../paper-ds-manage/references/versioning.md. During first setup, use its in-progress connection record; do not recursively rerun setup. Outside setup, a missing record needs paper-ds-setup.
3. Call get_font_family_info for every family before writing text. A missing weight falls back silently and breaks every measurement after it.
4. Call get_tokens and compare contentHash with the manifest. A different hash means tokens changed outside your session. Re-read before trusting names. Before overwriting artwork, checkpoint its real source, tokens, and any user's edits. Do not relabel a token-bound live frame as a frozen historical version.

Writing