feat(discovery): pursue bounded follow-up research

[drewstone]

Problem

KnowledgeDiscoveryWorker can return follow-up tasks, but the package only dispatches one batch. Products must otherwise rebuild recursive scheduling, limits, cancellation accounting, and task identity checks.

Solution

Add runDiscoveryLoop, a domain-neutral breadth-first runner that dispatches follow-ups with explicit round/task limits, retains pending work when stopped, returns partial work on cancellation, prevents cycles, and rejects incomplete dispatcher output. Search providers, agents, source verification, and candidate schemas remain product-owned worker concerns.

Verification

• pnpm typecheck
• pnpm lint
• pnpm test (218/218 passing; 10 network tests intentionally skipped)
• pnpm build
• Independent Opus review: APPROVE; cancellation-loss finding fixed and covered

[tangletools]

✅ Auto-approved drewstone PR — e5d19ae0

This PR was opened by the trusted drewstone account.
The full PR reviewer audit still runs separately and will publish findings if it detects issues.

_{tangletools · auto-approval · reason: drewstone_author · 2026-07-12T02:54:08Z}