Why: A fixed continuation cap and a 4096-token Anthropic fallback stopped long replies before the agent finished.
Evidence: go test ./runtime/ ./runtime/llm/
Impact: MaxLengthContinuations of 0 keeps the old cap of 3; a negative value removes it. Unset Anthropic max_tokens defaults to 128000.
Refs: feature/stream-display-overhaul
Co-authored-by: Cursor <cursoragent@cursor.com>