feat(repair): introduce focus bubble shroud for repair mini-game

Adds a dark expanding sphere around the repair model when the player
enters the immersive repair phases (fragmented / scanning / repairing /
reassembling). The bubble grows from 0 to 10m using GSAP expo.out over
2.5s and reverses on focus end, visually isolating the player from the
surrounding map.

- New useRepairFocusStore tracks active state + world center.
- New RepairFocusBubble renders a BackSide sphere shell + a soft cocoon
  decor pass (grid floor + directional light + ambient) inside.
- RepairGame drives setFocus from its lifecycle effect.
- Mounted in both GameStageContent and TestMap so behaviour matches in
  the production scene and the physics test scene.

Also drops the now-unused EBIKE_CONFIG_KEY constant in
GameStageContent.tsx (leftover from a previous remount-key strategy).

src/components/three/gameplay/RepairFocusBubble.tsx

@@ -0,0 +1,133 @@
+import { useEffect, useMemo, useRef } from "react";
+import gsap from "gsap";
+import * as THREE from "three";
+import { useRepairFocusStore } from "@/managers/stores/useRepairFocusStore";
+
+const BUBBLE_RADIUS_METERS = 10;
+const BUBBLE_GROW_DURATION_SECONDS = 2.5;
+const BUBBLE_SHRINK_DURATION_SECONDS = 1.2;
+const BUBBLE_COLOR = "#060814";
+const BUBBLE_OPACITY = 0.92;
+const BUBBLE_SHELL_RADIUS = 1; // sphere geometry baked at radius=1, scale = radius
+
+/**
+ * Dark sphere shroud rendered around the active repair model when the
+ * focus state is active. Grows from 0 -> BUBBLE_RADIUS_METERS using a
+ * GSAP `expo.out` ease so the player visually transitions from the open
+ * map to an isolated repair "cocoon". Reverses on focus end.
+ *
+ * The sphere uses BackSide rendering so the player remains inside the
+ * shroud when they stand near the repair model. A subtle decor pass
+ * (grid floor + soft directional light + light fog) is rendered as a
+ * sibling group so it appears once the bubble has expanded.
+ */
+export function RepairFocusBubble(): React.JSX.Element | null {
+  const active = useRepairFocusStore((state) => state.active);
+  const center = useRepairFocusStore((state) => state.center);
+  const groupRef = useRef<THREE.Group>(null);
+  const meshRef = useRef<THREE.Mesh>(null);
+  const decorRef = useRef<THREE.Group>(null);
+  const scaleRef = useRef({ value: 0.0001 });
+  const decorOpacityRef = useRef({ value: 0 });
+
+  const sphereGeometry = useMemo(
+    () => new THREE.SphereGeometry(BUBBLE_SHELL_RADIUS, 48, 32),
+    [],
+  );
+  const sphereMaterial = useMemo(
+    () =>
+      new THREE.MeshBasicMaterial({
+        color: BUBBLE_COLOR,
+        side: THREE.BackSide,
+        transparent: true,
+        opacity: BUBBLE_OPACITY,
+        depthWrite: false,
+        fog: false,
+      }),
+    [],
+  );
+
+  useEffect(() => {
+    return () => {
+      sphereGeometry.dispose();
+      sphereMaterial.dispose();
+    };
+  }, [sphereGeometry, sphereMaterial]);
+
+  useEffect(() => {
+    const targetScale = active ? BUBBLE_RADIUS_METERS : 0.0001;
+    const targetDecor = active ? 1 : 0;
+    const duration = active
+      ? BUBBLE_GROW_DURATION_SECONDS
+      : BUBBLE_SHRINK_DURATION_SECONDS;
+
+    const scaleTween = gsap.to(scaleRef.current, {
+      value: targetScale,
+      duration,
+      ease: active ? "expo.out" : "expo.in",
+      onUpdate: () => {
+        const mesh = meshRef.current;
+        if (mesh) mesh.scale.setScalar(scaleRef.current.value);
+      },
+    });
+
+    const decorTween = gsap.to(decorOpacityRef.current, {
+      value: targetDecor,
+      duration: duration * 0.8,
+      delay: active ? duration * 0.4 : 0,
+      ease: "power2.inOut",
+      onUpdate: () => {
+        const decor = decorRef.current;
+        if (!decor) return;
+        decor.traverse((child) => {
+          if (
+            child instanceof THREE.Mesh &&
+            child.material instanceof THREE.Material
+          ) {
+            const material = child.material as THREE.Material & {
+              opacity?: number;
+              transparent?: boolean;
+            };
+            if (typeof material.opacity === "number") {
+              material.opacity = decorOpacityRef.current.value;
+              material.transparent = true;
+            }
+          }
+        });
+      },
+    });
+
+    return () => {
+      scaleTween.kill();
+      decorTween.kill();
+    };
+  }, [active]);
+
+  // Render even when inactive so the shrink tween can play out; visibility
+  // is implicit via near-zero scale.
+  return (
+    <group ref={groupRef} position={center}>
+      <mesh
+        ref={meshRef}
+        geometry={sphereGeometry}
+        material={sphereMaterial}
+        renderOrder={-1}
+        frustumCulled={false}
+      />
+      <group ref={decorRef}>
+        {/* Subtle grid floor visible only inside the bubble */}
+        <gridHelper
+          args={[BUBBLE_RADIUS_METERS * 1.6, 24, "#1f2937", "#111827"]}
+          position={[0, -0.5, 0]}
+        />
+        {/* Soft directional light for the repair model */}
+        <directionalLight
+          position={[2, 4, 3]}
+          intensity={0.6}
+          color="#cbd5f5"
+        />
+        <ambientLight intensity={0.25} color="#1e293b" />
+      </group>
+    </group>
+  );
+}

src/components/three/gameplay/RepairGame.tsx

@@ -25,6 +25,7 @@ import type {
   RepairScannedBrokenPart,
 } from "@/types/gameplay/repairMission";
 import { useGameStore } from "@/managers/stores/useGameStore";
+import { useRepairFocusStore } from "@/managers/stores/useRepairFocusStore";
 import type { ModelTransformProps, Vector3Tuple } from "@/types/three/three";
 import { toVector3Scale } from "@/utils/three/scale";
 
@@ -110,6 +111,25 @@ export function RepairGame({
     };
   }, [mainState, mission, step]);
 
+  // Drive the global focus bubble: active during the immersive repair
+  // phases so the world dims/hides outside the dark sphere shroud.
+  const focusCenterX = snappedPosition[0];
+  const focusCenterY = snappedPosition[1];
+  const focusCenterZ = snappedPosition[2];
+  useEffect(() => {
+    const inFocusPhase =
+      mainState === mission && shouldFocusBubbleBeActive(step);
+    if (inFocusPhase) {
+      useRepairFocusStore
+        .getState()
+        .setFocus(true, [focusCenterX, focusCenterY, focusCenterZ]);
+      return () => {
+        useRepairFocusStore.getState().setFocus(false);
+      };
+    }
+    return undefined;
+  }, [mainState, mission, step, focusCenterX, focusCenterY, focusCenterZ]);
+
   useEffect(() => {
     if (mainState !== mission) return undefined;
 
@@ -214,6 +234,15 @@ function shouldKeepRepairRuntimeState(step: MissionStep): boolean {
   return step === "repairing" || step === "reassembling" || step === "done";
 }
 
+function shouldFocusBubbleBeActive(step: MissionStep): boolean {
+  return (
+    step === "fragmented" ||
+    step === "scanning" ||
+    step === "repairing" ||
+    step === "reassembling"
+  );
+}
+
 function getRepairMissionModelPaths(config: RepairMissionConfig): string[] {
   return [
     ...new Set([