fix: truncate large tool outputs to prevent Crof incomplete responses

Crof models (mimo, deepseek-v4-pro) return status=incomplete when
tool results contain too much text (e.g. full HTML pages at 8500+ tokens).
Auto-truncate tool outputs exceeding 8000 chars with truncation notice.
Combined with the 30-item conversation trim from previous commit.

CHANGELOG.md

@@ -9,6 +9,9 @@
   - Keeps system/developer messages, original user query, and most recent items
   - Drops oldest tool call/outputs from the middle when conversation grows too long
   - Prevents `status=incomplete` errors on providers with smaller context windows
+- **Truncates large tool outputs (>8000 chars)** to prevent model output token exhaustion
+  - Crof's models return `incomplete` when tool results contain too much text (e.g., full HTML pages)
+  - Truncated outputs include `[truncated N chars]` suffix so the model knows data was cut
 - Added request/response logging to `~/.cache/codex-proxy/requests.log` for debugging
 - Proxy stderr no longer discarded by launcher (visible in terminal for debugging)