1. Scope
   This profile defines the minimum required behavior for runtimes that execute tricu bundles.

2. Non-goals
   No tricu source parsing.
   No lambda elimination.
   No module system.
   No package manager.
   No local DB requirement.
   No authoring names beyond bundle exports.

3. Required bundle sections
   Header
   Manifest/exports
   Merkle nodes

4. Optional/skippable sections
   Source, debug, package metadata, signatures, provenance, etc.

5. Entrypoint selection
   Explicit export name first.
   Else export named main.
   Else single default root.
   Else error.

6. Node payload format
   Leaf/Stem/Fork byte layouts.

7. Hash verification
   Domain string and payload hashing rules.

8. Closure verification
   All referenced child hashes must exist.

9. Runtime representation
   Suggested JS representation, but not normative.

10. Reduction semantics
   The six Tree Calculus apply rules.

11. Codecs for v1
   Raw tree required.
   Maybe string/bool optional or experimental.

12. Required error cases
   Bad magic/version, missing export, hash mismatch, malformed payload, missing child.

13. Test fixtures
   List of bundles the implementation must pass.