Preserve aggregate state through SCF

[iangneal]

Summary

Preserves aggregate analysis state across SCF loops using the storage model from #649. This is PR 3 of 6 in the stacked series.

Related issues

No standalone issue; depends on #649.

Changes

• Carry aggregate state through scf.while operands, block arguments, conditions, yields, and results.
• Support resultless array writes/inserts, nested and dynamic writes, and static loop-index ranges.
• Conservatively fold reads and materialize small static nondeterministic arrays from final storage.
• Add focused regressions for array-of-POD loop state, nested writes, post-loop reads, and conservative intervals.

Testing

• git diff --check
• Focused SCF aggregate-state analysis regressions
• nix build -L on this exact stacked commit (371 lit tests plus the full unit/CAPI suite passed)

Submission checklist

• If I am an external contributor, this PR has a linked issue marked approved; otherwise, this does not apply.
• I added or updated tests for all relevant behavior, or explained above why tests are not needed.
• I updated the relevant TableGen or other documentation, or explained above why documentation is not needed.
• I added a changelog entry describing user-visible changes. (create-changelog in the Nix development shell creates a template.)
• I enabled Allow edits from maintainers if this PR comes from a fork.

AI assistance

• No AI tools contributed to this PR.
• AI tools contributed to this PR.

Tools used: OpenAI Codex.

How the tools contributed: Codex helped partition the original working-tree change, preserve dependency ordering, add focused regressions, and prepare this draft PR.

How I verified the contribution: Reviewed the isolated diff and ran git diff --check, the focused analysis regressions through the project test suite, and nix build -L on this exact commit.

[github-actions]

Test Results

  2 files  ±0    2 suites  ±0   8m 18s ⏱️ - 1m 33s
371 tests ±0  367 ✅ ±0  4 💤 ±0  0 ❌ ±0 
742 runs  ±0  734 ✅ ±0  8 💤 ±0  0 ❌ ±0 

Results for commit df58ee6. ± Comparison against base commit e845f58.

♻️ This comment has been updated with latest results.