fix: preserve keyboard focus and separate Space activation from voice

Keep focus visible across controls and stable during Contacts, Cockpit and mission roster updates. Preserve native short Space activation, and claim push-to-talk only after a 500 ms hold. Add panel Escape handling and keyboard-accessible attribution controls.

Retains the Map Source foundation contributed in https://github.com/bilawalsidhu/gods-eye-view/pull/171.

src/main.js

@@ -17,6 +17,7 @@ import militaryAwarenessLayer from './data/militaryAwareness.js';
 import localDataLayers from './data/localLayers.js';
 import { LAYER_STATE_REGISTRY } from './data/layerState.js';
 import { registerDataCredits } from './data/dataCredits.js';
+import { configureCreditKeyboardAccess } from './creditKeyboard.js';
 import { SceneDirector } from './scenes/director.js';
 import { initGevVoiceCommands } from './voice/gevRealtime.js';
 import { MapStackController } from './mapStackController.js';
@@ -131,6 +132,7 @@ async function init() {
     // expandable bottom-left credit lightbox (showOnScreen=false), so they never
     // clutter the on-globe line. See docs/pre-ship-audit-2026-07-01.md H11.
     registerDataCredits(viewer);
+    configureCreditKeyboardAccess(document);
 
     // Hide Cesium's default globe — Google Photorealistic 3D Tiles provide their own
     // globe at all LODs (street level → orbital). The default globe's 2D imagery