feat(output): auto-generated cover letter drafts per job

[bjridicodes]

One LLM call per APPLY job to generate custom cover letter draft. Stored next to job. Saves the most tedious part of applying.

[bjridicodes]

Relationships

Depends on:

• feat(output): tailored CV variants per high-score job #41 — cover letter uses the same tailored CV context; cannot run independently