Implement typed merge, bind, occurrences, paint, split, and group options

[HsiangNianian]

Parent

• [RFC-0001] OneRoll Program Language v2 #7

What to build

Implement typed collection transformations on RFC-0003 Values, RollSet references, immutable instruction history, and trace DAGs.

Frozen contract

• m(expr) combines explicit compatible collections and produces a merge trace node; bare m is invalid.
• b reads compatible completed instruction values, records source_instruction_ids, and never mutates ProgramResult history.
• o / o(N,S) returns ordered nested [value, count] Values with occurrence provenance.
• p[color:N,...] changes RollSet-view annotations and emits paint assignments without mutating RollNodes.
• y flattens one Values level or spreads compound draws while keeping node IDs.
• gN creates consecutive width-N nested Values with a final short remainder.

Acceptance criteria

• Every option matches RFC-0001 input/output and cardinality cases.
• Merge/bind preserve instruction IDs, trace inputs, and source-node identity.
• Occurrence order, selectors, paint normalization, split depth, and group remainder are deterministic.
• Empty RollSets retain item_kind; annotations do not alter scalar projection.
• Wrong-kind, zero, oversized, forward-bind, and incompatible requests return spanned RFC-0003 errors.
• Rust, installed Python, CLI JSON, and docs agree on schema-valid output.

Blocked by

• [RFC-0001] OneRoll Program Language v2 #7
• [RFC-0003] Typed Program Result, Roll Trace, and Error Contract #4
• Return structured parse, validation, and evaluation errors with spans #12
• Implement v2 keep, filter, sort, count, and unique option semantics #15
• Expose auditable traces for base, keep, and drop rolls #21
• Introduce typed values, inclusive ranges, and immutable variables #39
• Evaluate scoped validator expressions across filters and roll options #41