Real token streaming to hide the ~2s call (§14). Proxy emits its own minimal
NDJSON (delta/done/error); /dm/narrate becomes a 200 stream (422 stays sync,
model errors become an in-stream frame). Client reworks to an HTTPClient
poll-loop StreamTransport behind a testable seam; hold-back tag filter;
keep-partial mid-stream degrade; folds in the HttpTransport timeout fix.
Narrator first; NPC fast-follow.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>