stacks: parakeet healthcheck (curl→wget); qwen3-tts variant labels

- parakeet/compose.yaml: healthcheck was using curl which isn't in the
  image (only wget is, via apt). 2,190 failing checks — switched to
  `wget -q -O /dev/null`, container went healthy on recreate.
- qwen3-tts/.env.example: variant annotation was reversed. The upstream
  wrapper's runtime error is unambiguous: voice cloning requires the
  -Base variant, not -CustomVoice. Corrected the comment block and
  flipped the default to Qwen/Qwen3-TTS-12Hz-1.7B-Base.
- qwen3-tts/README.md: 0.6B switch snippet now suffixes -Base too,
  since plain `Qwen/Qwen3-TTS-12Hz-0.6B` isn't published on HF.

stacks/qwen3-tts/.env.example

@@ -26,13 +26,15 @@ QWEN3_TTS_BIND=0.0.0.0
 QWEN3_TTS_BACKEND=official
 
 # Model variant. Upstream publishes four checkpoints on HF:
-#   Qwen/Qwen3-TTS-12Hz-1.7B-CustomVoice — flagship, voice cloning
-#   Qwen/Qwen3-TTS-12Hz-1.7B-Base        — flagship, no cloning
-#   Qwen/Qwen3-TTS-12Hz-0.6B-CustomVoice — lightweight, voice cloning
-#   Qwen/Qwen3-TTS-12Hz-0.6B-Base        — lightweight, no cloning
+#   Qwen/Qwen3-TTS-12Hz-1.7B-Base        — flagship, supports voice cloning
+#   Qwen/Qwen3-TTS-12Hz-1.7B-CustomVoice — flagship, preset voices only
+#   Qwen/Qwen3-TTS-12Hz-0.6B-Base        — lightweight, supports voice cloning
+#   Qwen/Qwen3-TTS-12Hz-0.6B-CustomVoice — lightweight, preset voices only
 # 1.7B = ~6–8 GB VRAM bfloat16, best quality. 0.6B = ~2–3 GB.
-# Use -CustomVoice for `voice="clone:<name>"` to work.
-QWEN3_TTS_MODEL=Qwen/Qwen3-TTS-12Hz-1.7B-CustomVoice
+# `voice="clone:<name>"` only works with the -Base variants — that's
+# what the upstream wrapper enforces. Earlier versions of this file
+# had the variant labels reversed; corrected 2026-04-24.
+QWEN3_TTS_MODEL=Qwen/Qwen3-TTS-12Hz-1.7B-Base
 
 # Warm the model on container start so the first synthesis request
 # doesn't pay the load latency. Adds ~30 s to startup. Recommended.