feat: add privacy policy consistency checker

[gbasin]

Summary

• add docs/privacy-policy.md with machine-checkable privacy claims (PP-001..PP-006)
• add src/server/privacyPolicyChecker.ts with structured static checks for:
  • default DB/log persistence paths under ~/.agentboard
  • /api/paste-image temp-path behavior
  • denylisted telemetry/analytics dependencies
  • runtime network-call literal constraints (local-relative only)
  • Zustand persistence backed by safeStorage/localStorage
• add scripts/check-privacy-policy.ts CLI and privacy:check package script
• add src/server/__tests__/privacyPolicyChecker.test.ts
• gate bun run test by invoking bun run privacy:check in scripts/test-runner.ts
• document usage in README.md

Notes

• checker scope is static analysis only; it does not prove runtime behavior or legal compliance in all deployment configurations
• policy/checker IDs are intended to prevent drift between privacy promises and implementation over time

Validation

• bun run lint
• bun run typecheck
• bun run test