feat(company-monitoring): publish versioned events, impacts, corrections, and retractions

## Parent

#6002

## What to build

Publish current neutral material events and account-specific company impacts with append-only revisions, exact event-impact pairing, resumable fan-out, visible corrections and retractions, and bounded purge—without pointer or feed tables.

## Acceptance criteria

- [ ] Neutral events and company impacts use stable logical IDs, monotonic revisions, one current revision, lifecycle, and changed-at ordering.
- [ ] Every impact pins the exact neutral-event revision it was classified against and carries only the bounded ranked evidence selection.
- [ ] Duplicate decision fingerprints are idempotent and concurrent first publication yields exactly one current event and impact revision.
- [ ] Event and impact revision counters advance independently; per-company feedback or suppression cannot mutate shared event state.
- [ ] Neutral-event fan-out is resumable and renders consistent pinned revision pairs while old and new company projections coexist.
- [ ] Corrections and retractions remain latest current soft rows long enough for polling clients to converge.
- [ ] Company removal and terminal account purge delete only the owning account's state, retain deletion fencing until completion, and leave zero residual company content.
- [ ] Purge interruption resumes safely; another company's evidence, event, or impact cannot be deleted.
- [ ] Tests prove current-row uniqueness, revision monotonicity, bounded fan-out, latest-state correction/retraction behavior, and complete resumable purge.

## Blocked by

- #6011

Start by reading the parent issue #6002 and the blocking issue #6011; this issue names no files, entry points, or tests. Use the acceptance criteria as the completion checklist, including revision pairing, resumable fan-out, correction and retraction behavior, and account-scoped purge safety.

Written by the indexing model from the issue text.