feat(stats): wire stats server, overlay, and CLI into main process

- Stats server auto-start on immersion tracker init
- Stats overlay toggle via keybinding and IPC
- Stats CLI command (subminer stats) with cleanup mode
- mpv plugin menu integration for stats toggle
- CLI args for --stats, --stats-cleanup, --stats-response-path

src/renderer/state.ts

@@ -91,6 +91,7 @@ export type RendererState = {
   frequencyDictionaryBand5Color: string;
 
   keybindingsMap: Map<string, (string | number)[]>;
+  statsToggleKey: string;
   chordPending: boolean;
   chordTimeout: ReturnType<typeof setTimeout> | null;
   keyboardDrivenModeEnabled: boolean;
@@ -170,6 +171,7 @@ export function createRendererState(): RendererState {
     frequencyDictionaryBand5Color: '#8aadf4',
 
     keybindingsMap: new Map(),
+    statsToggleKey: 'Backquote',
     chordPending: false,
     chordTimeout: null,
     keyboardDrivenModeEnabled: false,