Add scheduled agent jobs

[jasonhedman]

Summary

• add durable one-time, interval, and timezone-aware calendar schedules through folder-based create/list/update tools
• run each occurrence in an isolated Eve task continuation so scheduled work never occupies the main Linq conversation
• persist structured worker outcomes from lifecycle events and immediately queue useful results back into the main Linq thread; nothing_to_report remains silent
• add occurrence uniqueness, missed-run policy, bounded worker restart, retry leases, and lease-token-safe report recovery
• prevent scheduled workers from calling send_message or react_to_message; the main conversation retains all native Linq messaging discretion

Dependency

• stacked on Add native agent messaging #101; this PR contains only the scheduled-task layer

Validation

• pnpm check (67 files, 286 tests; lint, types, format, Knip, and boundaries)
• DATABASE_URL_UNPOOLED=postgresql://postgres:postgres@127.0.0.1:54329/open_instinct pnpm db:check
• DATABASE_URL=postgresql://postgres:postgres@127.0.0.1:54329/open_instinct BETTER_AUTH_URL=http://localhost:3000 pnpm build:eve
• DATABASE_URL=postgresql://postgres:postgres@127.0.0.1:54329/open_instinct BETTER_AUTH_URL=http://localhost:3000 pnpm build