Building on PR #288's edit_message() abstraction:
- Telegram: edit_message_text() with MarkdownV2 + plain text fallback
- Discord: channel.fetch_message() + msg.edit() with length capping
- Slack: chat_update() via slack_bolt client
Also fixes the fallback regression in send_progress_messages() where
platforms that don't support editing would receive duplicated accumulated
tool lines. Now uses a can_edit flag — after the first failed edit, falls
back to sending individual lines (matching pre-PR behavior).
- Introduced new methods in run_agent.py for building API keyword arguments and normalizing assistant messages from API responses.
- Added functionality for compressing conversation context and managing session state in SQLite.
- Improved tool call execution handling, including enhanced logging and error management.
- Updated path handling in multiple platform files to utilize pathlib for better compatibility and readability.
- Introduced the `/new` command to start a new conversation, resetting the history.
- Updated command handling in the CLI and various platform adapters (Discord, Slack, Telegram) to support the new command.
- Added help command functionality to list available commands, improving user guidance.
- Enhanced command mapping for better integration across platforms, ensuring consistent command behavior.
