Track and reduce the no-new-error-throw suppression baseline

The committed ESLint suppression baseline needs a tracked reduction plan. At upstream commit `686a91971eccaec062b39830764b04e5d0aa8a03`, `eslint-suppressions.json` contains 274 `comfy/no-new-error-throw` suppressions across 90 files. The original review counted 282 across 92 files; the baseline has already shrunk, so that older count should not be used as the current target.

Assign a maintainer and agree a milestone for reducing the remaining baseline. Preserve the rule and existing error-reporting behavior; convert call sites in focused changes with relevant behavioral tests. Do not remove suppressions merely to move warnings elsewhere or weaken the rule.

Acceptance:

- Record an owner and an agreed milestone/date.
- Capture the current per-file suppression count and prevent unexplained growth.
- Track focused cleanup batches and show the count decreasing with lint and relevant tests passing.
- Document intentional exceptions with an accountable reviewer rather than silently refreshing the baseline.

This transfers review finding 07 F6 from the Sanity sandbox review to its upstream source. It is separate from the `src/lib` import-layer migration and does not claim the debt is fixed.

Start with eslint-suppressions.json at upstream commit 686a91971eccaec062b39830764b04e5d0aa8a03 and count the comfy/no-new-error-throw entries per file. Record an owner and milestone, then group focused cleanup batches while preserving error-reporting behavior. Done means the tracked count decreases, lint and relevant behavioral tests pass, and intentional exceptions have an accountable reviewer.

Written by the indexing model from the issue text.