The backend terminal tool (tools/terminal_tool.py) returns a single merged
'output' string plus 'exit_code' and 'error' — never 'stdout'/'stderr'.
ChatBubble was reading the non-existent 'stdout' key, so command output was
silently dropped and only the Duration footer showed.
- Parse 'output' as canonical; keep legacy 'stdout'/'stderr' fallback for
backward compat.
- Route terminal output into mainOutput so it renders like other tool bubbles.
- Surface non-zero exit codes as an error line when no 'error' string is set.
- Remove dead 'stderr' render branch.
- Update ToolBubbleParsingTest to assert the real payload shape (incl. the
exact issue-585 'echo hellp' sample) and add regression cases.
Co-authored-by: hy4ri <hy4ri@users.noreply.github.com>
