Implement RPG Player Character Movement System

## Overview
Create a comprehensive movement system for the player character in our RPG game using Godot. This system should provide smooth, responsive controls with typical RPG movement features.

## Requirements

### Basic Movement
- Implement 8-directional movement (up, down, left, right, and diagonals)
- Add smooth acceleration and deceleration
- Set appropriate walking speed with constant velocity
- Implement collision detection with environment objects

### Advanced Movement Features
- Add running/sprint ability (with speed multiplier when shift/designated key is held)
- Implement movement animations for different directions
- Add footstep sounds that vary based on terrain
- Include a small delay when changing directions for more natural movement

### Movement States
1. Idle State
- Default state when no movement input is detected
- Play idle animation based on last movement direction

2. Walking State
- Triggered by directional input
- Smooth transition from idle to walking animation
- Constant walking speed

3. Running State
- Activated by holding sprint key + directional input
- Increased movement speed
- Running animation with faster frames

### Technical Implementation Details
- Use Godot's built-in physics system for movement
- Implement using KinematicBody2D node
- Create state machine for handling different movement states
- Use Input.get_action_strength() for smooth analog controller support

### Code Structure
```gdscript
# Example structure for movement implementation
var speed = 100
var sprint_multiplier = 1.5
var acceleration = 0.1
var friction = 0.1
var velocity = Vector2.ZERO

func _physics_process(delta):
var input_vector = Vector2.ZERO
input_vector.x = Input.get_action_strength("ui_right") - Input.get_action_strength("ui_left")
input_vector.y = Input.get_action_strength("ui_down") - Input.get_action_strength("ui_up")
input_vector = input_vector.normalized()

# Movement logic here
```

## Acceptance Criteria
- [ ] Character moves smoothly in 8 directions
- [ ] Running/sprint functionality works correctly
- [ ] Proper collision detection with environment
- [ ] Smooth acceleration and deceleration
- [ ] Animation states change correctly based on movement
- [ ] Footstep sounds play appropriately
- [ ] Controls feel responsive and natural
- [ ] Code is well-documented and follows project standards
- [ ] Movement works with both keyboard and controller input

## Additional Notes
- Consider adding movement parameters that can be easily tweaked in the inspector
- Implement movement in a way that can be easily extended for different character types
- Add debug visualization for movement vectors and states during development

No project files, tests, or entry points are named. Start by locating the player scene and existing Godot movement code, then determine how the requested states, input actions, animations, terrain sounds, and collision behavior fit the project; done means the listed acceptance criteria work for keyboard and controller input.

Written by the indexing model from the issue text.