[rdlexporter] Fix register export on systemrdl-compiler 1.32.2

[hcallahan-lowrisc]

Summary

rdlexporter fails to export any block containing registers when resolved against systemrdl-compiler 1.32.2:

AttributeError: 'Reg' object has no attribute 'is_array'
  rdlexporter/exporter.py  RdlExporter._arrays

RdlExporter._arrays tested component.is_array, but that attribute was removed from the raw Component layer in systemrdl-compiler 1.32.2 by 25748b96c227 ("Remove .is_array from internal Component layer as it can be trivially derived"). The change is not mentioned in the 1.32.2 release notes, but its own docstring defined is_array as simply meaning "array_dimensions and array_stride are valid". Up to 1.32.1 the exporter relied on is_array being present on the Component objects it walks (rdlc.root.comp_defs).

Because the dependency is declared systemrdl-compiler~=1.32.1, a fresh resolve already picks up the broken 1.32.2 — e.g. the OpenTitan reggen integration that consumes this package.

Changes

• Fix: derive array-ness from component.array_dimensions (present with identical semantics in every supported systemrdl version; None for non-array components), exactly as upstream intends.
• Test: add test_cli_arrays_from_file — a round-trip snapshot covering both branches of _arrays (a plain register CTRL and a register array DATA[4]).

The dependency floor is intentionally left at systemrdl-compiler~=1.32.1: the fix works identically on 1.32.1 and 1.32.2, and raising the floor would break other consumers in the workspace that must stay on the older release. No pyproject.toml or uv.lock changes are included.

Verification

Against systemrdl-compiler 1.32.2:

• Without the fix, all three existing tests fail with the is_array AttributeError.
• With the fix: rdlexporter 4 passed, rdl2ot 5 passed, ruff clean, reuse lint compliant.
• Fix confirmed version-agnostic (also 4/4 on 1.32.1).

This PR includes AI-assisted content generated with Claude Code. All changes have been reviewed and are the responsibility of the listed author(s).