docs: add /mnt/work documentation + fix storage paths

- stem-split models dir: /mnt/work/models/audio-separator/
- stem-split output: /mnt/work/tmp/stem-splits/
- full docs at /mnt/work/docs/discord-feed-bots.md

src/tools/stem-split.ts

@@ -0,0 +1,90 @@
+/**
+ * Stem splitting tool using audio-separator (UVR5 models).
+ * Usage: bun run src/tools/stem-split.ts "artist - song name"
+ * 
+ * Pipeline:
+ * 1. Search + download audio via yt-dlp
+ * 2. Separate stems using audio-separator (MDX-Net/Roformer)
+ * 3. Output file paths for each stem
+ */
+
+import { $ } from 'bun';
+
+const OUTPUT_DIR = '/mnt/work/tmp/stem-splits';
+const MODEL_DIR = '/mnt/work/models/audio-separator';
+const MODEL = 'UVR-MDX-NET-Inst_HQ_3'; // High quality instrumental/vocal split
+
+async function searchAndDownload(query: string): Promise<string> {
+  console.error(`Searching: "${query}"...`);
+  const outPath = `${OUTPUT_DIR}/input.wav`;
+
+  await $`mkdir -p ${OUTPUT_DIR}`.quiet();
+
+  // Search youtube and download best audio
+  const result = await $`yt-dlp \
+    --extract-audio \
+    --audio-format wav \
+    --audio-quality 0 \
+    --output ${outPath} \
+    --no-playlist \
+    --default-search "ytsearch1" \
+    "${query}" 2>&1`.text();
+
+  console.error(result);
+
+  // yt-dlp might append .wav to the path
+  const { existsSync } = await import('fs');
+  if (existsSync(outPath)) return outPath;
+  if (existsSync(`${outPath}.wav`)) return `${outPath}.wav`;
+
+  throw new Error('Download failed - file not found');
+}
+
+async function splitStems(inputPath: string): Promise<string[]> {
+  console.error(`Splitting stems with ${MODEL}...`);
+
+  const result = await $`audio-separator \
+    --model_filename ${MODEL} \
+    --model_file_dir ${MODEL_DIR} \
+    --output_dir ${OUTPUT_DIR}/stems \
+    --output_format wav \
+    ${inputPath} 2>&1`.text();
+
+  console.error(result);
+
+  // Find output files
+  const { readdirSync } = await import('fs');
+  const stemDir = `${OUTPUT_DIR}/stems`;
+  const files = readdirSync(stemDir)
+    .filter(f => f.endsWith('.wav'))
+    .map(f => `${stemDir}/${f}`);
+
+  return files;
+}
+
+async function main() {
+  const query = process.argv.slice(2).join(' ');
+  if (!query) {
+    console.error('Usage: bun run src/tools/stem-split.ts "artist - song name"');
+    process.exit(1);
+  }
+
+  // Clean previous run
+  await $`rm -rf ${OUTPUT_DIR}`.quiet();
+
+  const inputPath = await searchAndDownload(query);
+  const stems = await splitStems(inputPath);
+
+  console.log(JSON.stringify({
+    query,
+    stems: stems.map(s => ({
+      path: s,
+      name: s.split('/').pop()?.replace('.wav', '') || s,
+    })),
+  }, null, 2));
+}
+
+main().catch(e => {
+  console.error(e);
+  process.exit(1);
+});