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/creditKeyboard.js

@@ -0,0 +1,70 @@
+/**
+ * Adds the keyboard semantics omitted by Cesium's href-less attribution links.
+ * Cesium retains ownership of showing and hiding its required credit lightbox.
+ */
+export function configureCreditKeyboardAccess(root = document) {
+  const expand = root?.querySelector?.('#cesium-credits .cesium-credit-expand-link');
+  const lightbox = root?.querySelector?.('.cesium-credit-lightbox');
+  const close = lightbox?.querySelector?.('.cesium-credit-lightbox-close');
+  if (!expand || !lightbox || !close) return false;
+  const overlay = lightbox.parentElement;
+
+  if (!lightbox.id) lightbox.id = 'cesium-credit-lightbox';
+  expand.setAttribute('role', 'button');
+  expand.setAttribute('tabindex', '0');
+  expand.setAttribute('aria-haspopup', 'dialog');
+  expand.setAttribute('aria-controls', lightbox.id);
+  expand.setAttribute('aria-expanded', 'false');
+  close.setAttribute('role', 'button');
+  close.setAttribute('tabindex', '0');
+  close.setAttribute('aria-label', 'Close data attribution');
+
+  if (expand.dataset.gevKeyboardReady === 'true') return true;
+  expand.dataset.gevKeyboardReady = 'true';
+
+  const installKeyboardActivation = (control) => {
+    let spacePressed = false;
+    control.addEventListener('keydown', (event) => {
+      if (event.key === 'Enter') {
+        event.preventDefault();
+        if (!event.repeat) control.click();
+        return;
+      }
+      if (event.key !== ' ') return;
+      event.preventDefault();
+      if (!event.repeat) spacePressed = true;
+    });
+    control.addEventListener('keyup', (event) => {
+      if (event.key !== ' ') return;
+      event.preventDefault();
+      if (!spacePressed) return;
+      spacePressed = false;
+      control.click();
+    });
+    // A long Space hold may hand control to push-to-talk and move focus away.
+    // Cancelling the armed release prevents that eventual keyup from also
+    // activating the attribution control.
+    control.addEventListener('blur', () => { spacePressed = false; });
+  };
+  const closeAndRestoreFocus = () => {
+    expand.setAttribute('aria-expanded', 'false');
+    expand.focus();
+  };
+  installKeyboardActivation(expand);
+  installKeyboardActivation(close);
+  lightbox.addEventListener('keydown', (event) => {
+    if (event.key !== 'Escape' || event.defaultPrevented) return;
+    event.preventDefault();
+    event.stopPropagation();
+    close.click();
+  });
+  expand.addEventListener('click', () => {
+    expand.setAttribute('aria-expanded', 'true');
+    close.focus();
+  });
+  close.addEventListener('click', closeAndRestoreFocus);
+  overlay?.addEventListener?.('click', (event) => {
+    if (!lightbox.contains(event.target)) closeAndRestoreFocus();
+  });
+  return true;
+}