feat(voices): canonical voice corpus + dots.tts-optimized refs

Engine-agnostic voice corpus: canonical source clip + transcript per voice,
per-engine reference sets derived by derive.py from engines.yaml profiles.
First residents donut/glados/emmie/miranda optimized + verified clean for
dots.tts (sentence-bounded ref + accurate transcript — dots leaks reference
audio into output otherwise). canonical/ + transcripts/ tracked; derived/
gitignored (regenerable). Records the dots.tts burn-in in persistent-memory.

voices/engines.yaml

@@ -0,0 +1,40 @@
+# Per-engine reference requirements. derive.py reads this to turn a canonical
+# source + transcript into an engine-ready reference set under derived/<engine>/.
+#
+# Fields:
+#   sample_rate          native SR the engine wants
+#   resample             true = derive.py should resample to sample_rate
+#                        (NOTE: resample is a follow-up — see the resample TODO
+#                         in derive.py; dots resamples internally so it's false there)
+#   needs_transcript     engine requires a per-reference transcript file
+#   ref_max_seconds      cap on derived reference length (null = uncapped)
+#   ref_sentence_bounded transcript/clip must end on a sentence boundary (. ! ?)
+#                        — set for engines that leak reference content otherwise
+
+engines:
+  dots:
+    description: "dots.tts (rednote-hilab) — continuous-AR 48kHz zero-shot clone"
+    sample_rate: 48000
+    resample: false          # runtime auto-resamples at load; keep source SR
+    needs_transcript: true   # REQUIRED and must be accurate + sentence-bounded
+    ref_max_seconds: 10
+    ref_sentence_bounded: true
+    notes: >
+      Transcript accuracy AND sentence-boundary are load-bearing: a mismatched or
+      mid-clause transcript makes dots regurgitate reference audio into the output.
+
+  chatterbox:
+    description: "chatterbox-fast (Turbo) — streaming 24kHz clone"
+    sample_rate: 24000
+    resample: true
+    needs_transcript: false  # audio-only clone; server globs its refs dir live
+    ref_max_seconds: null
+    ref_sentence_bounded: false
+
+  zonos:
+    description: "Zonos2 — expressive 44.1kHz clone + emotion dials"
+    sample_rate: 44100
+    resample: true
+    needs_transcript: false
+    ref_max_seconds: null
+    ref_sentence_bounded: false