v0.3.0

Legion just became better and more stable!

Changes

• Replace share_bindings boolean with binding_scope (:iteration, :turn, :conversation) for fine-grained control over variable lifetime across code executions
• Add action_types/0 callback to restrict which actions an agent can use (e.g. ~w(return done) for read-only agents)
• Add max_message_length config with truncation support to prevent unbounded message growth
• Add multimedia message support: {:image, data, media_type}, {:image_url, url}, and {:multipart, parts}
• Add Legion.get_messages/1 to retrieve conversation history from a running agent
• Expand AgentTool with parallel/2, pipeline/1, then/3, and extra_allowed_modules/0 for sub-agent orchestration; sub-agents are auto-aliased in the sandbox
• Generate dynamic AgentTool.description/0 from sub-agent moduledocs
• Move system prompt resolution to AgentPrompt, respecting custom system_prompt/0 overrides
• Validate config keys at startup with warnings for unknown keys
• Add @moduledoc compile-time validation via __before_compile__
• Harden sandbox: block def/defp/__ENV__, additional :erlang functions (process_flag, list_to_atom, system_info), catch throws and exits, surface compiler diagnostics on errors
• Handle executor exceptions gracefully instead of crashing the agent loop
• Add Calendar to sandbox safe-module list
• Emit :exception telemetry events for iteration, LLM, and sandbox spans; use System.convert_time_unit/3 for duration reporting
• Extensive new test coverage for AgentServer, Executor, Sandbox, and ASTChecker