* feat: add tool output auto-truncation at framework level (#110)
Prevent context blowup from large tool outputs by adding opt-in
character-based truncation (head 70% + tail 30% with marker).
Agent-level `maxToolOutputChars` and per-tool `maxOutputChars`
with per-tool taking priority. Marker overhead is budgeted so
the result never exceeds the configured limit.
* fix: truncateToolOutput may exceed maxChars when limit < marker overhead
- Fall back to hard slice when maxChars is too small to fit the marker
- Fix misplaced JSDoc for outputSchema in AgentConfig
- Tighten test assertion to verify length <= maxChars
JackChen
MrAvalonApple
Ibrahim Kazimov