Broken planes cannot fly; repair heals gradually (ISS-089)

- flyPlane 409s a broken plane (health <= 0) before any refuel math — fuel/cash untouched
- engine auto-chain skips chaining when a landing's wear breaks the plane (queue kept intact)
- finishRepairs heals along round(f x 100) each tick; flip to available at exactly 100 on gate pass
- repairPlane no longer jumps health to 100 — it starts the gradual heal
- REMOVED BROKEN_BURN_MULTIPLIER / conditionBurnMultiplier and all burn sites (unreachable now)
- OpenAPI + route comments reworded; unit tests reworked; e2e maintenance.spec.ts per issue
- v0.45.0

lib/game/catalog.ts

@@ -128,15 +128,6 @@ export const MAX_FUEL_DISCOUNT = 0.2;
 // ponytail: balance-tunable — health lost per km of landed legs (~130 mid-range EDDF↔LEMD hops to break from full; 1/10× slower since v0.43.0, ISS-085).
 export const WEAR_PER_KM = 0.0005;
 
-// ponytail: balance-tunable — burn multiplier for a broken plane (health ≤ 0): it still flies, just thirsty.
-export const BROKEN_BURN_MULTIPLIER = 1.5;
-
-// Broken-state burn factor for one plane's health — the third multiplicative term alongside wind at every
-// per-plane burn site (flyPlane dispatch top-up + backstop, engine landed fuel + auto-chain, live display).
-export function conditionBurnMultiplier(health: number): number {
-  return health <= 0 ? BROKEN_BURN_MULTIPLIER : 1;
-}
-
 // ponytail: balance-tunable — flat repair cost in € (per-type if balance demands it).
 export const REPAIR_COST = 1_500;
 // ponytail: balance-tunable — how long a repair grounds the plane, sim ms (3 game days).