fix(cli): use 'where' instead of 'which' on Windows for FFmpeg and br… (#336)

* fix(cli): use 'where' instead of 'which' on Windows for FFmpeg and browser detection

- findFFmpeg() now uses 'where ffmpeg' on Windows, 'which ffmpeg' on Unix
- whichBinary() now uses 'where' on Windows, 'which' on Unix

Fixes FFmpeg detection failure on Windows where 'which' command doesn't exist.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* fix(cli): handle multi-line output from Windows 'where' command

Windows 'where' can return multiple paths (one per line) when there
are multiple matches on PATH. Take only the first non-empty line.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

* fix(cli): extend Windows 'where' fix to whisper, tts, and clipboard modules

- whisper/manager.ts: whichBinary() now uses 'where' on Windows
- tts/synthesize.ts: findPython() now uses 'where' on Windows
- utils/clipboard.ts: detectProvider() now uses 'where' on Windows

All functions handle multi-line output from 'where' command.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

packages/cli/src/whisper/manager.ts

@@ -22,12 +22,17 @@ function getModelUrl(model: string): string {
 
 function whichBinary(name: string): string | undefined {
   try {
-    const result = execFileSync("which", [name], {
+    const cmd = process.platform === "win32" ? "where" : "which";
+    const output = execFileSync(cmd, [name], {
       encoding: "utf-8",
       stdio: ["pipe", "pipe", "pipe"],
       timeout: 5000,
-    }).trim();
-    return result || undefined;
+    });
+    const first = output
+      .split(/\r?\n/)
+      .map((s) => s.trim())
+      .find(Boolean);
+    return first || undefined;
   } catch {
     return undefined;
   }