Initial commit: akai-fetch - AKAI sampler ISO downloader & extractor

- fetch: Go CLI tool for searching, downloading, and extracting
  AKAI sampler ISOs from archive.org
- scripts/extract_wavs.sh: Shell script driving akaiutil to
  convert samples to WAV
- Dockerfile: Multi-stage build packaging akaiutil + fetch
- third_party/akaiutil: Vendored akaiutil v4.6.7 source (GPLv2)
- docs/akaiutil.md: Full akaiutil reference

.gitignore

@@ -0,0 +1,28 @@
+# Binaries
+fetch
+akai-fetch
+akai-fetch-bin
+*.exe
+
+# Original akaiutil source (vendored copy in third_party/)
+akaiutil-4.6.7/
+
+# Build artifacts
+*.o
+*.obj
+
+# Data
+*.iso
+output/
+wavs
+
+# IDE
+.vscode/
+.idea/
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Temp
+/tmp/