Fix unsupported index type errors in common range-indexing workflows

[magland]

Category

Common script semantics and indexing correctness

Problem

RunMat can raise MATLAB:UnsupportedIndexType in ordinary range-indexing workflows inside real scripts.

Intent

This should be treated as a runtime/indexing correctness issue affecting common script execution, not as a one-off script-specific bug.

Done When

• the reported real-script indexing pattern no longer fails with UnsupportedIndexType
• the underlying indexing semantics are corrected rather than patched for a single script
• representative regression coverage exists for the failing indexing form