claude --resume keeps the model's prior context but emits no past
turns over stream-json, so the pane was visually empty until the
user sent a new prompt. The orchestrator now reads the last 256 KB
of the on-disk transcript JSONL when SpawnSpec.resume is true and
seeds the ConversationController with the parsed items before the
stream subscription starts. Best-effort: missing or unreadable file
just falls back to the previous empty-pane behaviour.
Co-Authored-By: Claude <noreply@anthropic.com>
