Prevent restarting haptic playback from gamepad/keyboard while a clip plays

[tomaabe]

Summary

While a clip is playing, the Play WASAPI (L1) and Play XAudio2 (R1) buttons could still be retriggered via the controller or the keyboard, restarting playback from the beginning or starting the other engine. Only mouse clicks were correctly blocked. This change gates both play actions on !IsPlaying() for every input path.

Repro steps

1. Build and run the Advanced Haptics sample.
2. Connect a controller and select a multi-second clip.
3. Start playback, then while it is still playing:
   • Press the controller L1/R1 again → playback restarts from the beginning (bug).
   • With R1 activated by keyboard Space, the button keeps focus; pressing Space again retriggers it (bug).
   • Start L1 while R1 is playing (or vice versa) → both play (bug).
   • Mouse clicks on the buttons are correctly ignored (expected).

Root cause

The play buttons were wrapped in ImGui::BeginDisabled(IsPlaying()), but BeginDisabled only suppresses mouse interaction. The gamepad shortcut (|| IsButtonPressed(...)) bypassed the disabled state entirely, and ImGui still activates keyboard Space/Enter on a button that already had focus, so playback could be retriggered through those paths.

Fix

• Always draw the buttons (ImGui requires the call every frame) but gate each play action on !isPlaying so mouse, keyboard (Space/Enter) and gamepad (L1/R1) paths are all blocked while a clip is playing, and the two engines are mutually exclusive.
• Call ImGui::SetWindowFocus(nullptr) when playback starts so the now-disabled button does not keep showing a pressed animation when Space is held.

Testing

• Built Debug|x64 with Visual Studio.
• Verified L1/R1 cannot retrigger playback mid-clip from mouse, keyboard or controller; that the two engines are mutually exclusive; that the buttons re-enable after a clip finishes; and that the pressed animation no longer lingers when Space is held on a disabled button.

Notes

• UI-only change contained to haptics.cpp; no public API changes.

[BrianPeekMSFT]

Fixed internally, will be in the next github publish.