Document that local dev needs BOTH servers running

Link to the split @dossier/docs surface dev-origin-aware (same-origin in prod, docs dev origin in dev) via an SSOT $lib/docs module — NOT a Vite dev proxy, which two Vite dev servers cannot share one origin for adopted dev-origin-aware linking to the split @dossier/docs surface (no dev proxy — two Vite dev servers can't share one origin). The consequence: in dev, the app's docs links resolve against the docs dev origin (http://localhost:4321), so the docs dev server must also be running, or the links fail to load. This atom tracks documenting that requirement.

Why a task, not a fix-in-place

The fix is genuine authored content — a dev-onboarding note (where to put it: a root dev-script note vs. a new packages/app/README.md that doesn't exist yet) requiring the Principal SvelteKit Engineer's judgment about placement and phrasing. The log-auditor surfaced it from DEC-0048's named Consequence and files it so the follow-up is durable and owned rather than a sentence in a reply. confidence: inferred (agent-derived from the decision's named follow-up, not human-curated).

Done-definition

See acceptance_criteria. Keep it SSOT — the why (the two-Vite-dev-servers-one-origin module-namespace collision) already lives in Link to the split @dossier/docs surface dev-origin-aware (same-origin in prod, docs dev origin in dev) via an SSOT $lib/docs module — NOT a Vite dev proxy, which two Vite dev servers cannot share one origin for and the packages/app/vite.config.ts NOTE comment; the doc should point at $lib/docs + that NOTE, not restate the rationale.

Board globbed before filing — no open task covered documenting the dev-server requirement.