Canonical IO-list encoding of a Dsxir.RuntimeProgram used as the input to the SHA-256 content hash that becomes the program's :version.

Determinism rules:

• Map keys are sorted alphabetically before being encoded.
• Atoms are encoded as binaries to avoid coupling to the BEAM atom table.
• Tuples are encoded as ["__tuple__", elems...].
• Non-semantic fields are excluded — description on FieldSpec and on the program's metadata. Other metadata is included.
• Node and edge order is significant and is preserved verbatim.
• Predicate strings are encoded verbatim; the parsed AST is not part of the hash.
• Inline Dsxir.Signature.Compiled structs are encoded by their fields list plus :instruction. Module-atom signatures are encoded by their fully-qualified atom name.
• Strings escape " as \".