feat(input): add hold-to-auto-swing for mouse fire

[f1cklepickle]

Why

• PC attack currently depends on click frequency, while Android supports hold-to-repeat.
• This creates control inconsistency and caps practical DPS by user click speed.

Proposed Change

• Add a desktop hold-fire path so holding LMB continuously requests attacks.
• Route hold requests through the same authoritative attack cooldown gate used by existing fire logic.
• Preserve single-click behavior and avoid behavior regressions in UI interaction.

Acceptance Criteria

• Holding LMB triggers repeated attacks without repeated clicking.
• Attack cadence while holding is governed by effective attack rate, not frame rate.
• Existing single-click attacks still work.
• Android hold-fire behavior remains unchanged.

Testing / Validation

• Manual:
  • In MainPrototype, hold LMB with unarmed and sword equipped.
  • Verify repeat attacks occur and cadence scales with weapon attack speed.
• Automated:
  • EditMode: add/input tests for hold intent generation and cooldown-gated repeats.
  • PlayMode: add smoke test for hold-to-repeat attack cadence.

Context (Optional)

• Related: feat(combat): wire weapon attackSpeed to MobileInputDriver attack rate #145
• Milestone: P3 Core Gameplay