Pi 0.84.4 fixes sessions, tool-context bugs

This is a quietly important reliability release: Pi is making long-running, extensible agent workflows safer before adding more surface area.

• –Prevents resumed JSONL sessions from corrupting subsequent entries.
• –Compacts oversized tool results before sending the next provider request, reducing context-related failures.
• –Adds `clear_queue` and UI prompt events for more precise RPC integrations and host-state tracking.
• –Terminal capability overrides and fullscreen copy controls improve portability across terminal environments.
• –Vertex proxy, OpenRouter reasoning, and fragmented Mistral tool-call fixes strengthen multi-provider workflows.