feat(company-monitoring): add a lazy portfolio monitoring workspace

## Parent

#6002

## What to build

Deliver one lazy-loaded native workspace for portfolio onboarding, current material impacts, evidence, confidence, coverage, corrections, and retractions without adding a dashboard panel or eager data-loader domain.

## Acceptance criteria

- [ ] A compact launcher opens one lazy singleton workspace with Companies and Events views.
- [ ] Companies supports direct add, browser-parsed CSV batches of at most 100 rows, import progress, pause, remove, retry, and claim confirmation.
- [ ] Events provides server-paginated list and detail views with direction, affected channel, magnitude, confidence rationale, bounded evidence, correction/retraction state, and coverage context.
- [ ] Required states include empty portfolio, awaiting first scan, adequate quiet, events observed, partial/stale/unavailable coverage, needs confirmation, provider capped, correction, retraction, partial import failure, and mutation timeout reconciliation.
- [ ] snapshot_required automatically resnapshots while preserving filters and valid selection, closes removed detail, restores accessible focus, and exposes an error only when recovery fails.
- [ ] Entitlement lapse stops polling and clears account-scoped client data immediately; unpurged reactivation takes a fresh snapshot and post-purge reactivation starts explicit onboarding.
- [ ] CSV content and progress remain local only for the active upload; sign-out and account switch leave no retained portfolio content.
- [ ] Tests cover 500-row pagination, replay-safe partial imports, concurrent removal, failed resnapshot, keyboard and screen-reader flow, mobile overflow, and bounded network/data behavior.

## Blocked by

- #6014

## Promotion gate

Implementation may be prepared behind the UI flag, but activation and issue completion require both Stage 1 arms: the two-customer historical-usefulness result and the fourteen-day live-operability tracer.

Start with parent issue #6002 and blocker #6014, then trace the compact launcher and the Companies and Events views described here. Treat the acceptance criteria as the completion checklist, including lazy loading, required states, account-data cleanup, recovery behavior, accessibility, and the listed tests; activation also depends on both Stage 1 promotion arms.

Written by the indexing model from the issue text.