feat(game): skill XP on task completion + power bands in duration (#45)

lib/game/skills.ts

@@ -1,6 +1,8 @@
 // Pure skill-progression module (spec §6): XP accrual, level→power, titles. No lib/db imports — operates on plain SkillRow data (Task 12's crew_skills table); the frontend imports it for the CREW-tab display.
-import type { SkillName } from './crew-costs'
-import { POWER_BANDS, XP_THRESHOLDS } from './crew-costs'
+import { ACTION_SKILL, POWER_BANDS, XP_THRESHOLDS, type SkillName } from './crew-costs'
+import type { CrewMember } from './crew'
+import type { CrewDto } from './save'
+import type { TaskType } from './tasks'
 export interface SkillRow {
   saveId: string
   crewId: string
@@ -51,3 +53,15 @@ export function grantXp(
   }
   return { rows, events }
 }
+
+// The duration formula's powerOf (Task 1) driven by the skill band (PR B, §6): each member's
+// power is the band of that member's level in the action's skill (ACTION_SKILL[type]). Names
+// map to crew ids (unique per single-player save); an unknown member or a missing row falls
+// back to L0 → power 1 (Task 1's default). Called by save.ts's makePowerOfFor (the queueing
+// routes) and — once /api/crew carries each member's skill rows — by the team builder's live
+// preview (Task 15).
+export function makePowerOf(roster: CrewDto[], skillRows: SkillRow[], type: TaskType): (m: CrewMember) => number {
+  const idByName = new Map(roster.map((c): [string, string] => [c.name, String(c.id)]))
+  const levelByCrew = new Map(skillRows.filter((r) => r.skill === ACTION_SKILL[type]).map((r): [string, number] => [r.crewId, r.level]))
+  return (m) => powerForLevel(levelByCrew.get(idByName.get(m.name) ?? '') ?? 0)
+}