kokoro: persist custom voices across container recreate

Wrapper only enumerates one voice directory (settings.voices_dir,
default /app/api/src/voices/v1_0 — inside the container's writable
layer, not bind-mounted). Override via VOICES_DIR=/app/user_voices
(host bind mount) and add a command shim that cp -r's built-ins from
the in-image v1_0 into user_voices on every start. Built-ins re-seed
fresh from the image (so upgrades that add voices propagate); custom
.pt files in user_voices are preserved (cp -r is additive).

Also adds scripts/blend_kokoro_voice.py + a playbook around it that
mirrors the wrapper's request-time voice="a(w)+b(w)" math but writes
the result as a named .pt to user_voices, making it discoverable via
GET /v1/audio/voices and persistent across recreate. Defaults to
athena = af_bella(2)+af_aoede(1) normalized.

playbooks/blend-kokoro-voice.yaml

@@ -0,0 +1,78 @@
+# Blend two or more Kokoro voicepacks into a new persistent voice.
+#
+# Mirrors the wrapper's request-time `voice="a(w)+b(w)"` blend op
+# (api/src/services/tts_service.py::_get_voices_path) — same math,
+# but the result is written to /worktank/kokoro/user_voices/ on the
+# host (bind-mounted into the container at /app/user_voices, which
+# the compose's VOICES_DIR env points the wrapper at). Result:
+#   - immediately appears in GET /v1/audio/voices
+#   - usable as voice="<out_name>" in /v1/audio/speech
+#   - persistent across `up --force-recreate` and image upgrade
+#     (it's on the host bind mount, not the container layer)
+#
+# Requires the persistent-voices compose layout (entrypoint shim +
+# VOICES_DIR=/app/user_voices). If the deployed compose predates that,
+# run `scripts/elway irv-ml1 --playbook playbooks/deploy-kokoro.yaml`
+# first to roll it out.
+#
+# Usage (defaults to athena = af_bella(2)+af_aoede(1) normalized):
+#   scripts/elway irv-ml1 --playbook playbooks/blend-kokoro-voice.yaml
+#
+# Override per-run:
+#   scripts/elway irv-ml1 --playbook playbooks/blend-kokoro-voice.yaml \
+#     --var 'recipe=af_bella(1)+am_adam(1)' --var out_name=androgyne
+#
+# Re-run with --var force=1 to overwrite an existing voice.
+
+vars:
+  recipe: "af_bella(2)+af_aoede(1)"
+  out_name: athena
+  user_voices_dir: /worktank/kokoro/user_voices
+  container: kokoro
+  script_local: scripts/blend_kokoro_voice.py
+  script_host: /tmp/blend_kokoro_voice.py
+  script_in_container: /tmp/blend_kokoro_voice.py
+  force: "0"
+  api_port: "8193"
+
+steps:
+  - name: Upload blend script to host /tmp
+    upload:
+      src: "{{ script_local }}"
+      dest: "{{ script_host }}"
+      mode: "0755"
+
+  - name: Copy script into kokoro container
+    shell: docker cp {{ script_host }} {{ container }}:{{ script_in_container }}
+
+  - name: Run blend inside container
+    # `-u 0`: host /worktank/kokoro/user_voices is chowned to 1001:1001
+    # (appuser) by deploy-kokoro.yaml; we still write as root so the
+    # output is plainly 0644 root:root and the wrapper (running as
+    # appuser) can read it. Also avoids any UID-mapping subtlety.
+    # --force is wired through a shell switch so we can stay inside
+    # elway's plain {{ var }} substitution (no jinja conditionals).
+    shell: |
+      FORCE_FLAG=""
+      if [ "{{ force }}" = "1" ]; then FORCE_FLAG="--force"; fi
+      docker exec -u 0 {{ container }} python {{ script_in_container }} \
+        --recipe '{{ recipe }}' --out '{{ out_name }}' $FORCE_FLAG
+    when: "[ ! -f {{ user_voices_dir }}/{{ out_name }}.pt ] || [ '{{ force }}' = '1' ]"
+
+verify:
+  - name: Output .pt exists on host (persistent)
+    shell: test -s {{ user_voices_dir }}/{{ out_name }}.pt
+    changed_when: "false"
+
+  - name: Voice appears in /v1/audio/voices
+    shell: curl -sf http://localhost:{{ api_port }}/v1/audio/voices | grep -q '"{{ out_name }}"'
+    changed_when: "false"
+
+  - name: Synthesize a probe sample (no playback)
+    shell: |
+      curl -sf -X POST http://localhost:{{ api_port }}/v1/audio/speech \
+        -H 'Content-Type: application/json' \
+        -d '{"model":"kokoro","input":"Hello, I am {{ out_name }}.","voice":"{{ out_name }}","response_format":"wav"}' \
+        -o /tmp/{{ out_name }}-probe.wav \
+        && test -s /tmp/{{ out_name }}-probe.wav
+    changed_when: "false"