Add runtime deadzone configuration API

[Copilot]

Describe your changes

Deadzones were previously baked into AxisAsButton model definitions. This PR adds runtime deadzone configuration per player/axis.

New API on GameInputPlayer:

• setDeadzone(path, value) - Configure deadzone at runtime (value: 0.0-1.0)
  • Stick-level: 'leftStick', 'rightStick', 'trigger'
  • Axis-level: 'leftStick.x', 'leftStick.y', 'trigger.left', etc.
• getDeadzone(path) - Query current deadzone
• resetDeadzone(path?) - Clear overrides

Implementation:

• Runtime overrides stored in private Map<string, number>
• Modified getStickVector(), getNormalizedStickVector(), getNormalizedTriggerValue() to check for overrides before using model defaults
• Runtime values take precedence; falls back to model-defined deadzones when unset

Example:

const player = gameInput.getPlayer(0);

// Per-stick configuration
player.setDeadzone('leftStick', 0.15);

// Per-axis fine-tuning
player.setDeadzone('leftStick.x', 0.2);
player.setDeadzone('trigger.left', 0.25);

// Query and reset
const dz = player.getDeadzone('leftStick.x');  // 0.2
player.resetDeadzone('leftStick');

Use cases: Accessibility settings, worn controller compensation, precision gaming, per-game preferences.

Describe your testing

Added 23 test cases covering:

• API validation (bounds checking, invalid paths)
• Stick/axis-level configuration
• Integration with getStickVector() and getNormalizedStickVector()
• Backward compatibility (no runtime overrides)
• Override priority

All 2177 tests passing. CodeQL scan clean.

Issue ticket number and link

#[issue number]

Checklist before requesting a review

• I have performed a self-review of my code
• The code passes lint checks.
• The code has been tested for regressions of existing features.
• I have considered adding unit tests for any new code.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add per-axis deadzone configuration API</issue_title>
<issue_description>## Feature Request
Allow developers to set deadzone values for each player/axis at runtime, rather than baking them into AxisAsButton definitions.

Current Limitation

Deadzones are hardcoded in axis definitions:

// src/axis-as-button.js
constructor (direction, axisNum, max = 1, deadZone = 0.25) {
    // ❌ Deadzone is set at model definition time
    this.deadZone = direction === '+' ? deadZone : -deadZone
}

Users cannot adjust sensitivity per-player or at runtime.

Proposed API

// Get player
const player = gameInput.getPlayer(0)

// Set deadzone for entire stick
player.setDeadzone('leftStick', 0.15)

// Set deadzone for individual axis
player.setDeadzone('leftStick.x', 0.2)
player.setDeadzone('leftStick.y', 0.1)

// Get current deadzone
const dz = player.getDeadzone('leftStick')  // Returns 0.15

// Reset to default
player.resetDeadzone('leftStick')

Advanced Options

// Different deadzone shapes
player.setDeadzone('leftStick', {
    threshold: 0.15,
    shape: 'radial'  // or 'axial', 'cross'
})

// Per-player defaults
gameInput.setDefaultDeadzone(0.2)  // All players, all axes

// Save/load user preferences
const prefs = player.getDeadzonePreferences()
localStorage.setItem('deadzones', JSON.stringify(prefs))

Implementation Approach

1. Add deadzone property to GameInputPlayer
2. Store per-axis overrides in player state
3. Apply runtime deadzones in update loop
4. Maintain backward compatibility with model-defined deadzones

Use Cases

• Accessibility: Users with motor impairments need custom deadzones
• Worn controllers: Older controllers with stick drift need larger deadzones
• Precision gaming: Competitive players want minimal deadzones
• Per-game settings: Different games need different sensitivities

Example: Settings Menu

// In-game deadzone calibration
function showDeadzoneSettings(playerIndex) {
    const player = gameInput.getPlayer(playerIndex)
    
    slider.oninput = (e) => {
        const value = e.target.value / 100  // 0.0 to 1.0
        player.setDeadzone('leftStick', value)
        updatePreview()
    }
}

Backward Compatibility

• Default to model-defined deadzones if not overridden
• Runtime overrides are optional
• No breaking changes to existing API
  </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add per-axis deadzone configuration API #72

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