fix(worker): let progressing repository scans complete

[ecryptoguru]

Summary

• remove elapsed-time engine termination for Quick, Standard, and Deep repository scans
• use the existing bounded run.json sequence/turn/phase receipt as the durable progress signal
• retain provider budget limits, user cancellation, and a 20-minute no-progress stop
• keep URL/API egress limits and bounded optional triage unchanged
• correct runtime documentation so 15/45 minute figures are estimates, not repository cutoffs

Verification

• pnpm exec vitest run apps/worker/src/engine/runner.test.ts apps/worker/src/jobs/run-scan.job.test.ts
• pnpm test:core
• pnpm typecheck
• pnpm lint
• pnpm format:check
• git diff --check