Execute semicolon-separated Programs across Rust, Python, and CLI

[HsiangNianian]

Parent

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

What to build

Move semicolon execution onto the accepted typed Engine and RFC-0003 ProgramResult without regressing compatibility roll() or run().

Frozen contract

• Strict Engine.roll accepts exactly one Instruction and returns InstructionResult; Engine.run accepts source text and returns ProgramResult.
• Top-level instructions are source ordered and share one request-wide RollNode/TraceNode pool, RNG, immutable environment, deadline/token, and budget.
• Each InstructionResult has a unique activation ID, frame-local index, byte span, canonical text, typed value, scalar projection, trace root, and nested executions.
• Repeat iterations, selected branches, and function bodies remain under their activating instruction instead of flattening into top-level history.
• Program comment is decoded text or null in strict v2; metadata records compatibility mode and replay descriptor.
• Any instruction failure atomically returns one structured exception/error envelope and no completed prefix.
• Module-level roll/run retain v1 dictionaries through adapters over the same Engine.

Acceptance criteria

• Engine.run("1d6; 2d6 # encounter") returns two ordered typed instructions plus Program metadata.
• Engine.roll rejects separators and returns one typed InstructionResult.
• Rust, installed Python objects, to_dict(), and CLI JSON validate against RFC-0003 and agree on ordering and IDs.
• Nested indices, spans, trace roots, values, and read-only collections satisfy graph invariants.
• All instructions share one RFC-0002 ExecutionContext and counter set.
• Empty instructions and mid-Program failures return structured atomic errors.
• Compatibility roll() and run() retain legacy dictionaries through Engine adapters.

Blocked by

• [RFC-0001] OneRoll Program Language v2 #7 human acceptance
• [RFC-0003] Typed Program Result, Roll Trace, and Error Contract #4 human acceptance
• [RFC-0004] Python Engine API and Package Boundary #5 human acceptance
• Introduce typed values, inclusive ranges, and immutable variables #39