feat(core): implement playable CTF prototype with 6 core scripts

Implements the minimal playable core for the teaser prototype:
- Game.cs: Bootstrap, scene setup, scoring, round reset, win condition
- Unit.cs: Movement, route following, tagging, respawn
- RouteDrawer.cs: Click-drag route input with LineRenderer preview
- Flag.cs: Pickup, drop, return mechanics
- Visibility.cs: Fog of war via SpriteRenderer visibility
- SimpleAI.cs: Enemy AI that chases player flag

All game objects created programmatically (no Editor setup required).
Uses RuntimeInitializeOnLoadMethod for automatic bootstrap.

Co-Authored-By: Claude <noreply@anthropic.com>

Backyard CTF/Assets/Scripts/RouteDrawer.cs

@@ -0,0 +1,147 @@
+using System.Collections.Generic;
+using UnityEngine;
+using UnityEngine.InputSystem;
+
+public class RouteDrawer : MonoBehaviour
+{
+    Unit selectedUnit;
+    List<Vector2> currentRoute = new();
+    LineRenderer lineRenderer;
+    bool isDrawing;
+
+    const float MinPointDistance = 0.5f;
+
+    void Start()
+    {
+        CreateLineRenderer();
+    }
+
+    void CreateLineRenderer()
+    {
+        var lineGO = new GameObject("RouteLine");
+        lineRenderer = lineGO.AddComponent<LineRenderer>();
+        lineRenderer.startWidth = 0.15f;
+        lineRenderer.endWidth = 0.15f;
+        lineRenderer.material = new Material(Shader.Find("Sprites/Default"));
+        lineRenderer.startColor = new Color(1f, 1f, 1f, 0.5f);
+        lineRenderer.endColor = new Color(1f, 1f, 1f, 0.5f);
+        lineRenderer.sortingOrder = 20;
+        lineRenderer.positionCount = 0;
+    }
+
+    void Update()
+    {
+        var mouse = Mouse.current;
+        var touch = Touchscreen.current;
+
+        // Handle mouse input
+        if (mouse != null)
+        {
+            HandlePointerInput(
+                mouse.leftButton.wasPressedThisFrame,
+                mouse.leftButton.wasReleasedThisFrame,
+                mouse.leftButton.isPressed,
+                mouse.position.ReadValue()
+            );
+        }
+        // Handle touch input
+        else if (touch != null && touch.primaryTouch.press.isPressed)
+        {
+            var primaryTouch = touch.primaryTouch;
+            HandlePointerInput(
+                primaryTouch.press.wasPressedThisFrame,
+                primaryTouch.press.wasReleasedThisFrame,
+                primaryTouch.press.isPressed,
+                primaryTouch.position.ReadValue()
+            );
+        }
+    }
+
+    void HandlePointerInput(bool pressed, bool released, bool held, Vector2 screenPos)
+    {
+        Vector2 worldPos = Camera.main.ScreenToWorldPoint(screenPos);
+
+        if (pressed)
+        {
+            OnPointerDown(worldPos);
+        }
+        else if (released)
+        {
+            OnPointerUp();
+        }
+        else if (held && isDrawing)
+        {
+            OnPointerDrag(worldPos);
+        }
+    }
+
+    void OnPointerDown(Vector2 worldPos)
+    {
+        // Check if we clicked on a player unit
+        var hit = Physics2D.OverlapPoint(worldPos);
+        if (hit != null)
+        {
+            var unit = hit.GetComponent<Unit>();
+            if (unit != null && unit.team == Unit.Team.Player && !unit.isTaggedOut)
+            {
+                selectedUnit = unit;
+                isDrawing = true;
+                currentRoute.Clear();
+                currentRoute.Add(worldPos);
+                UpdateLineRenderer();
+            }
+        }
+    }
+
+    void OnPointerDrag(Vector2 worldPos)
+    {
+        if (!isDrawing || selectedUnit == null) return;
+
+        // Only add point if far enough from last point
+        if (currentRoute.Count > 0)
+        {
+            float dist = Vector2.Distance(currentRoute[currentRoute.Count - 1], worldPos);
+            if (dist >= MinPointDistance)
+            {
+                currentRoute.Add(worldPos);
+                UpdateLineRenderer();
+            }
+        }
+    }
+
+    void OnPointerUp()
+    {
+        if (isDrawing && selectedUnit != null && currentRoute.Count > 0)
+        {
+            // Remove the first point (unit's current position) and apply route
+            if (currentRoute.Count > 1)
+            {
+                currentRoute.RemoveAt(0);
+            }
+            selectedUnit.SetRoute(currentRoute);
+        }
+
+        // Clear drawing state
+        isDrawing = false;
+        selectedUnit = null;
+        currentRoute.Clear();
+        ClearLineRenderer();
+    }
+
+    void UpdateLineRenderer()
+    {
+        if (lineRenderer == null) return;
+
+        lineRenderer.positionCount = currentRoute.Count;
+        for (int i = 0; i < currentRoute.Count; i++)
+        {
+            lineRenderer.SetPosition(i, new Vector3(currentRoute[i].x, currentRoute[i].y, 0));
+        }
+    }
+
+    void ClearLineRenderer()
+    {
+        if (lineRenderer == null) return;
+        lineRenderer.positionCount = 0;
+    }
+}