Pre-v1.4.41 prompts lived in two homes — `src/lib/ai/prompts/` (per-
metric system prompts + safety contracts) and `src/lib/insights/prompt
*.ts` (user-prompt builder + comparison snapshot + the `compactSections`
helper). A new reader could not tell from filenames which file to
extend; both directories looked equally authoritative. Audit rec #3
flagged the split as the only undiscoverable seam in the AI layer.
Move both files into `src/lib/ai/prompts/`:
- `lib/insights/prompt.ts` → `lib/ai/prompts/insight-system-prompt.ts`
- `lib/insights/prompt-compact.ts` → `lib/ai/prompts/compact-sections.ts`
- co-located tests follow
Three importers updated: `app/api/insights/generate/route.ts`,
`lib/ai/coach/snapshot.ts`, the generate route test (the
`vi.mock('@/lib/insights/prompt')` path moved too). Prompts now have
ONE home and ONE mental model.
