engine: uncomment vector.xmile integration test after #355 #358

Problem

The vector.xmile integration test in src/simlin-engine/tests/simulate.rs (line 869) is commented out and must remain disabled until two dependencies are resolved:

1. Cross-dimension VECTOR ELM MAP support: The test uses VECTOR ELM MAP(b[B1], a[DimA]) where the source array b is subscripted by dimension B, but it's used in a context where dimension A is expected. The compiler cannot resolve this dimension mismatch. This requires either element-level subscript flattening or a new cross-dimension indexing strategy.

2. VM support for vector operations: The vector operations (VECTOR SELECT, VECTOR ELM MAP, VECTOR SORT ORDER) and ALLOCATE AVAILABLE are currently implemented only in the interpreter, not in the VM bytecode compiler/executor (issue engine: vector operations and ALLOCATE AVAILABLE are interpreter-only, not in VM #355).

The vector_simple subset (which avoids cross-dimension indexing) passes via the separate simulates_vector_simple_mdl test.

Why it matters

• Completeness: The full vector.xmile test represents real-world use cases and must pass before the feature is considered complete.
• Test coverage: Integration tests ensure end-to-end correctness for complex features; leaving this disabled hides gaps in the VM implementation.

Component(s) affected

• src/simlin-engine/tests/simulate.rs (test suite)
• src/simlin-engine/src/compiler/ (dimension checking/inference)
• src/simlin-engine/src/vm.rs (vector operation opcodes, once engine: vector operations and ALLOCATE AVAILABLE are interpreter-only, not in VM #355 is complete)

Acceptance criteria

This test can be uncommented and enabled once:

1. Issue engine: vector operations and ALLOCATE AVAILABLE are interpreter-only, not in VM #355 (VM vector operations) is resolved and all vector operations have VM support.
2. Cross-dimension VECTOR ELM MAP indexing is supported by the compiler (new issue to be filed if not already tracked).

Then:

• Uncomment the test at line 869 in simulate.rs
• Run the full test suite to confirm it passes
• Remove any related comments explaining why it was disabled

Context

Identified while reviewing test coverage in src/simlin-engine/tests/simulate.rs after the MDL full-compat merge.