[codex] Replace mpv fullscreen toggle with launch mode config (#48)

Co-authored-by: bee <autumn@skerritt.blog>

src/shared/mpv-launch-mode.ts

@@ -0,0 +1,24 @@
+import type { MpvLaunchMode } from '../types/config';
+
+export const MPV_LAUNCH_MODE_VALUES = ['normal', 'maximized', 'fullscreen'] as const satisfies
+  readonly MpvLaunchMode[];
+
+export function parseMpvLaunchMode(value: unknown): MpvLaunchMode | undefined {
+  if (typeof value !== 'string') {
+    return undefined;
+  }
+
+  const normalized = value.trim().toLowerCase();
+  return MPV_LAUNCH_MODE_VALUES.find((candidate) => candidate === normalized);
+}
+
+export function buildMpvLaunchModeArgs(launchMode: MpvLaunchMode): string[] {
+  switch (launchMode) {
+    case 'fullscreen':
+      return ['--fullscreen'];
+    case 'maximized':
+      return ['--window-maximized=yes'];
+    default:
+      return [];
+  }
+}