refactor(ebike): drop redundant 'locked' substate, single entry trigger

The ebike mission previously had two redundant entry-point sub-states
('locked' and 'waiting') that were behaviorally identical from the
player's perspective:
- both showed the same 'Lancer le Repair Game' prompt
- both allowed the press-E handler in Ebike.tsx to jump to 'inspected'

In addition, the locked state caused two latent bugs:
- the static-map ebike node (GameMap) and the live <Ebike> component
  were rendered simultaneously at the same world position
- a generic RepairMissionTrigger anchor sphere was rendered in
  parallel to Ebike's own InteractableObject (two triggers, same area)

Changes:
- useGameStore: ebike's initial currentStep + completeIntroState target
  is now 'waiting' (pylon/farm still init at 'locked' — they need it).
- Ebike.tsx: drop dead === 'locked' branches in repairGameOwnsEbikeModel
  and the press-E handler.
- EbikeRepairNarrator: only reset the played-set on 'waiting'.
- RepairGame: drop 'locked' from the ebike livePosition guard.
- REPAIR_MISSION_TRIGGERS: empty array (the duplicate ebike anchor
  sphere is gone). Keep the array + RepairMissionTrigger component for
  future re-use.
- GameMap: hide the static-map ebike node as soon as
  mainState === 'ebike' (was: only when ebikeStep !== 'locked').
- repairMissionState.getPreviousMissionStep: ebike rewinds from
  'waiting' to 'waiting' (cap), pylon to 'npc-return', farm to 'locked'.

The 'locked' value is intentionally kept in the MissionStep type union
because the farm mission still uses it as a meaningful kickoff state
driving FarmNarrativeFlow's auto-transition to electricienne_history.

src/components/game/EbikeRepairNarrator.tsx

@@ -17,8 +17,8 @@ import { playDialogueById } from "@/utils/dialogues/playDialogue";
  * - `done`        -> "Eeeet voilà! Il fonctionne comme une horloge!..."
  *
  * Each cue is one-shot per mission run; the played-set resets when the
- * mission state rolls back to `locked`/`waiting` so debug-panel replays
- * still trigger the narration.
+ * mission state rolls back to `waiting` so debug-panel replays still
+ * trigger the narration.
  *
  * Audio AND subtitles are strictly scoped to `mainState === "ebike"`. If
  * the player leaves the ebike main state mid-line (debug panel jump,
@@ -46,7 +46,7 @@ export function EbikeRepairNarrator(): null {
   const activeAudioRef = useRef<HTMLAudioElement | null>(null);
 
   useEffect(() => {
-    if (ebikeStep === "locked" || ebikeStep === "waiting") {
+    if (ebikeStep === "waiting") {
       playedRef.current.clear();
     }
   }, [ebikeStep]);