fix: checkpoint research requests before submission

[ga1ien]

Outcome

• writes a private mode-0600, fsynced request checkpoint before the first paid submission
• records the accepted durable run immediately and supports explicit reattachment after SIGINT/process loss
• releases @braintied/research 0.8.2 with updated operator guidance

Verification

• 57/57 unit and contract tests
• 8/8 Instagram/Bright Data tests
• TypeScript, CJS/ESM build, and clean tarball consumer
• production dependency audit: 0 vulnerabilities
• Gitleaks: no findings
• archive SHA-256: cbb5fa5d255914728a213085dc3b0e379e7da678901538d9576e46b99f47e155