A live capture against claude 2.1.150 (both --print and the interactive
stream-json transport clide uses) confirms --include-partial-messages
emits the in-progress reply as stream_event envelopes wrapping Anthropic
streaming deltas — NOT assistant events with partial:true, which is what
T-168 assumed, so that handler never fired and streaming was inert.
Replace it: accumulate content_block_delta text per message id (tracked
from message_start, since deltas carry no id) and emit a placeholder under
a stable partial-<id> uuid the controller upserts in place; the matching
single-text-block assistant event reuses that uuid to finalize, while
tool_use / thinking blocks keep their own uuids and append in order. Tests
rewritten against the captured shape; spike doc records it.
T-184.
Co-Authored-By: Claude <noreply@anthropic.com>