Post-alpha: distinguish [%s] arrays from %s lists in dim expansion (generated-API break)

[Pranav-s79]

Domain council finding: TIMER[%s] (true C/svd2rust array) and TIMER%s (individual members) expand to identical names, so a vendor converting between the two — a compile break for all generated-code consumers — produces no findings. Fix direction: is_array flag on DimInfo + a BREAKING rule. Listed in the RULES.md "does not check" section until then.

🤖 Generated with Claude Code

[Pranav-s79]

Reopening to correct the tracking state before the 0.1.0a1 alpha ships.

The dim render-style distinction — [%s] (true generated array) versus %s (individual member registers) — is not implemented in 0.1.0a1: both styles expand to identical flattened names, so converting between them still produces no findings. The limitation is deliberate for the alpha and is documented in RULES.md → "What regdrift does not check (yet)", which links this issue as its status.

This issue was previously closed as completed, which falsely implied the gap was fixed. It is reopened as post-alpha work so the RULES.md status link stays truthful. It does not block the public alpha: the false-green is explicitly disclosed, and the fix direction (an is_array flag on DimInfo plus a BREAKING rule) remains as described above.