vibevoice + chatterbox: fix build refs (full 40-char SHA + chatterbox dockerfile path)

Both deploys failed against irv-ml1 today with upstream-changed-on-us
errors:

* vibevoice: VIBEVOICE_SHA=7614c469a145 (12-char short) made docker
  buildx report "repository does not contain ref 7614c469a145" — same
  commit IS still HEAD of main, but buildx's git source resolver
  doesn't accept short hashes even when unambiguous. Now full 40-char.

* chatterbox: dockerfile: docker/Dockerfile.gpu — devnen restructured
  the repo to put Dockerfiles at root, renamed by CUDA version
  (Dockerfile.cu128, .cpu, .rocm). Switched to Dockerfile.cu128 (GPU
  build for CUDA 12.8 toolkit; works on irv-ml1's 595.58.03 driver).
  Also pinned CHATTERBOX_SHA to a full 40-char SHA instead of `main`
  so future upstream churn doesn't break the deploy without warning.

Live host .env files patched directly (the playbook only seeds .env
when absent, so canonical edits don't propagate to existing installs).

stacks/chatterbox/.env.example

@@ -3,9 +3,11 @@
 
 # ── build pin ────────────────────────────────────────────────────────
 # SHA of devnen/Chatterbox-TTS-Server. Bump + rebuild when you want
-# upstream wrapper updates. Pin a SHA — the wrapper has no tagged
-# releases yet.
-CHATTERBOX_SHA=main
+# upstream wrapper updates. Use the FULL 40-char SHA — docker buildx's
+# git source resolver doesn't accept short hashes. Pinning to a SHA
+# (rather than `main`) protects against upstream churn — the previous
+# `main` value broke when devnen restructured docker/ paths in repo.
+CHATTERBOX_SHA=68213e75c248f4f4bbd185f7c20ec02722fdc79b
 
 # Local image tag — bump when you change build context to force a
 # fresh layer build.