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/cli/help.test.ts

@@ -18,6 +18,7 @@ test('printHelp includes configured texthooker port', () => {
   assert.match(output, /--help\s+Show this help/);
   assert.match(output, /default: 7777/);
   assert.match(output, /--launch-mpv/);
+  assert.match(output, /--stats\s+Open the stats dashboard in your browser/);
   assert.match(output, /--refresh-known-words/);
   assert.match(output, /--setup\s+Open first-run setup window/);
   assert.match(output, /--anilist-status/);