feat(stats): add stats server, API endpoints, config, and Anki integration

- Hono HTTP server with 20+ REST endpoints for stats data
- Stats overlay BrowserWindow with toggle keybinding
- IPC channel definitions and preload bridge
- Stats config section (toggleKey, serverPort, autoStartServer, autoOpenBrowser)
- Config resolver for stats section
- AnkiConnect proxy endpoints (guiBrowse, notesInfo)
- Note ID passthrough in card mining callback chain
- Stats CLI command with autoOpenBrowser respect

src/main/runtime/stats-cli-command.ts

@@ -0,0 +1,99 @@
+import fs from 'node:fs';
+import path from 'node:path';
+import type { CliArgs, CliCommandSource } from '../../cli/args';
+import type { VocabularyCleanupSummary } from '../../core/services/immersion-tracker/types';
+
+type StatsCliConfig = {
+  immersionTracking?: {
+    enabled?: boolean;
+  };
+  stats: {
+    serverPort: number;
+    autoOpenBrowser?: boolean;
+  };
+};
+
+export type StatsCliCommandResponse = {
+  ok: boolean;
+  url?: string;
+  error?: string;
+};
+
+export function writeStatsCliCommandResponse(
+  responsePath: string,
+  payload: StatsCliCommandResponse,
+): void {
+  fs.mkdirSync(path.dirname(responsePath), { recursive: true });
+  fs.writeFileSync(responsePath, JSON.stringify(payload, null, 2), 'utf8');
+}
+
+export function createRunStatsCliCommandHandler(deps: {
+  getResolvedConfig: () => StatsCliConfig;
+  ensureImmersionTrackerStarted: () => void;
+  ensureVocabularyCleanupTokenizerReady?: () => Promise<void> | void;
+  getImmersionTracker: () => { cleanupVocabularyStats?: () => Promise<VocabularyCleanupSummary> } | null;
+  ensureStatsServerStarted: () => string;
+  openExternal: (url: string) => Promise<unknown>;
+  writeResponse: (responsePath: string, payload: StatsCliCommandResponse) => void;
+  exitAppWithCode: (code: number) => void;
+  logInfo: (message: string) => void;
+  logWarn: (message: string, error: unknown) => void;
+  logError: (message: string, error: unknown) => void;
+}) {
+  const writeResponseSafe = (
+    responsePath: string | undefined,
+    payload: StatsCliCommandResponse,
+  ): void => {
+    if (!responsePath) return;
+    try {
+      deps.writeResponse(responsePath, payload);
+    } catch (error) {
+      deps.logWarn(`Failed to write stats response: ${responsePath}`, error);
+    }
+  };
+
+  return async (
+    args: Pick<CliArgs, 'statsResponsePath' | 'statsCleanup' | 'statsCleanupVocab'>,
+    source: CliCommandSource,
+  ): Promise<void> => {
+    try {
+      const config = deps.getResolvedConfig();
+      if (config.immersionTracking?.enabled === false) {
+        throw new Error('Immersion tracking is disabled in config.');
+      }
+
+      deps.ensureImmersionTrackerStarted();
+      const tracker = deps.getImmersionTracker();
+      if (!tracker) {
+        throw new Error('Immersion tracker failed to initialize.');
+      }
+
+      if (args.statsCleanup) {
+        await deps.ensureVocabularyCleanupTokenizerReady?.();
+        if (!args.statsCleanupVocab || !tracker.cleanupVocabularyStats) {
+          throw new Error('Stats cleanup mode is not available.');
+        }
+        const result = await tracker.cleanupVocabularyStats();
+        deps.logInfo(
+          `Stats vocabulary cleanup complete: scanned=${result.scanned} kept=${result.kept} deleted=${result.deleted} repaired=${result.repaired}`,
+        );
+        writeResponseSafe(args.statsResponsePath, { ok: true });
+        return;
+      }
+
+      const url = deps.ensureStatsServerStarted();
+      if (config.stats.autoOpenBrowser !== false) {
+        await deps.openExternal(url);
+      }
+      deps.logInfo(`Stats dashboard available at ${url}`);
+      writeResponseSafe(args.statsResponsePath, { ok: true, url });
+    } catch (error) {
+      deps.logError('Stats command failed', error);
+      const message = error instanceof Error ? error.message : String(error);
+      writeResponseSafe(args.statsResponsePath, { ok: false, error: message });
+      if (source === 'initial') {
+        deps.exitAppWithCode(1);
+      }
+    }
+  };
+}