fix(kokoro): Download phonemization model during installation (#9165)

Signed-off-by: Richard Palethorpe <io@richiejp.com>

Author: richiejp

backend/python/kokoro/install.sh

@@ -21,3 +21,8 @@ if [ "x${BUILD_PROFILE}" == "xl4t12" ]; then
 fi
 
 installRequirements
+
+# spaCy is a dependency of misaki (used by kokoro for English phonemization).
+# Pre-download the model here because at runtime the portable Python environment
+# has no pip/uv, so spacy's auto-download would fail.
+python -m spacy download en_core_web_sm