API and Worker runtime paths are inconsistent

[simplerjiang]

• Source: .automation/sprint.md V041-DEBT-2.
• Impact: Source, packaged desktop, and worker processes may resolve data/frontend/PDF paths differently.
• Repro:
  1. Compare AppRuntimePaths behavior in API and worker.
  2. Validate source and packaged runtime directories.
• Expected: API and Worker share a documented runtime path contract.
• Actual: Debt records path inconsistency.
• Claim: Assign backend/desktop owner.
• Repair: Centralize runtime path rules and document source vs packaged behavior.
• Verification: Unit tests for path resolution plus packaged smoke if runtime paths change.