Require agent disclosure when policy is disclose

[zaguzovmaksim0-hue]

What changed

• require a non-empty agent disclosure whenever agentPolicy is disclose
• add a database-free regression test covering omitted disclosure and a valid supervised disclosure

Why

/api/v1/jobs/:slug/apply-schema publishes disclosure.required: true for disclose jobs, but the validator only rejected agent === null when the caller had supplied an agent key. Omitting the key entirely therefore bypassed the published contract.

Before the fix:

validateApplication(schema, { name: 'Ada' }, 'disclose')
=> ok: true, agent: null

After the fix, the same input returns the existing agent validation problem.

Tests

• node --test test/applications.test.ts — pass
• pnpm test — pass on Android/Termux; database-dependent API suite skips when local Postgres is unavailable, as designed

Closes #70