fix(audio): seek after -i (output-side) so drag-seek works on non-seekable HTTP CDNs

Input-side fast seek (-ss before -i) requires the HTTP server to support
Range/keyframe seeking. NetEase's CDN (music.126.net signed streams) doesn't,
so dragging the progress bar hung FFmpeg and the player force-killed it
(SIGKILL) with no audio. Moving -ss after -i decodes from the start and
discards to the target, which works on any HTTP stream; FFmpeg still fast-seeks
when the CDN supports it, so QQ keeps its instant resume.

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

src/audio/player.test.ts

@@ -55,13 +55,13 @@ describe("buildFfmpegArgs", () => {
     expect(idx).toBeLessThan(args.indexOf("-i")); // input options must precede -i
   });
 
-  it("inserts -ss before -i when seekSeconds > 0", () => {
+  it("inserts -ss after -i when seekSeconds > 0", () => {
     const args = buildFfmpegArgs("https://example.com/song.mp3", 42);
     const ssIdx = args.indexOf("-ss");
     const iIdx = args.indexOf("-i");
     expect(ssIdx).toBeGreaterThan(-1);
     expect(args[ssIdx + 1]).toBe("42");
-    expect(ssIdx).toBeLessThan(iIdx);
+    expect(ssIdx).toBeGreaterThan(iIdx);
   });
 
   it("does not insert -ss when seekSeconds is 0", () => {

src/audio/player.ts

@@ -103,8 +103,10 @@ export function buildFfmpegArgs(url: string, seekSeconds: number): string[] {
       "-reconnect_on_http_error", "4xx,5xx",
     );
   }
+  args.push("-i", url);
+  // Output-side seek (after -i): works on CDNs that reject Range/keyframe seeks (NetEase music.126.net).
   if (seekSeconds > 0) args.push("-ss", String(seekSeconds));
-  args.push("-i", url, "-f", "s16le", "-ar", "48000", "-ac", "2", "-acodec", "pcm_s16le", "-");
+  args.push("-f", "s16le", "-ar", "48000", "-ac", "2", "-acodec", "pcm_s16le", "-");
 
   return args;
 }