feat(api): ship + research endpoints queue tasks with lead + helpers; mission accept is instant and free (#44)

lib/game/research.ts

@@ -70,6 +70,23 @@ export async function resolveResearchTask(db: GameDb, task: Task): Promise<void>
   await persist(db)
 }
 
+// The research pre-checks, extracted for the queueing route (5a(ii)): the same codes and
+// messages as researchTech — unknown tech (404), already researched (409), missing prereqs
+// (409, naming what is missing). The cost check stays out: the queueing path deducts at
+// queue time (queueTask) and the research lands when the task completes on the tick.
+export async function checkResearchPreconditions(db: GameDb, techId: number): Promise<void> {
+  await ensureSave(db)
+  const rows = await db.db.select().from(schema.tech)
+  const target = rows.find((t) => t.id === techId)
+  if (!target) throw new ResearchError(404, `Unknown tech ${techId}`)
+
+  const def = TECHS.find((t) => t.slug === target.slug)!
+  const researched = await researchedSlugs(db)
+  if (researched.has(def.slug)) throw new ResearchError(409, `${def.name} is already researched`)
+  const missing = def.prereqs.filter((p) => !researched.has(p)).map((slug) => TECHS.find((t) => t.slug === slug)?.name ?? slug)
+  if (missing.length > 0) throw new ResearchError(409, `${def.name} requires ${missing.join(' and ')} first`)
+}
+
 // Research one tech: validates prerequisites (409, naming what is missing) and the cost (422),
 // spends it from the cargo hold, then delegates the unlock to the resolver at the new turn.
 export async function researchTech(db: GameDb, techId: number): Promise<TechDto[]> {