refactor(editor): extract gen-audio-* handlers into cli_gen_audio.cpp

main.cpp had grown past 28k lines, with each new procedural-
generation command adding 100-200 lines to the inline if/else
dispatch chain. This commit starts breaking that up by moving
the four audio-related handlers (--gen-audio-tone, -noise,
-sweep, --gen-zone-audio-pack) into their own translation unit.

Pattern established here for future family extractions:

- Family lives in cli_<family>.{hpp,cpp}
- Single dispatch entry point: bool handle<Family>(int& i, int argc,
  char** argv, int& outRc) — true if matched (writes outRc), false
  to fall through.
- main.cpp's argv loop calls each family's dispatcher first and
  returns its outRc on match, before the legacy in-line chain.

Side-benefit: consolidated the duplicated 25-line WAV header
writer + 5ms attack/release envelope into shared helpers
(writeWavMono16, applyEdgeEnvelope) at the top of the new file.

main.cpp drops from 28,943 → 28,329 lines (-614). Audio family
is fully self-contained (~440 lines), behavior unchanged
(verified by re-running tone/noise/sweep + zone-audio-pack).

tools/editor/cli_gen_audio.hpp

@@ -0,0 +1,20 @@
+#pragma once
+
+namespace wowee {
+namespace editor {
+namespace cli {
+
+// Dispatch the four --gen-audio-* / --gen-zone-audio-pack handlers.
+//
+// Returns true if argv[i] matched one of these flags; in that case
+// outRc holds the exit code (0 success, non-zero failure) and main()
+// should `return outRc` immediately. Returns false if no match —
+// caller should continue its dispatch chain.
+//
+// On match, advances `i` past the consumed arguments (same semantics
+// as the in-line handlers it replaces).
+bool handleGenAudio(int& i, int argc, char** argv, int& outRc);
+
+} // namespace cli
+} // namespace editor
+} // namespace wowee