Lifecycle Hooks Plugin (SuperPi.Extension behaviour).

Implements lifecycle hook interception for workspace sessions:

• Discovers and merges hooks.json files across workspace .agents/hooks.json and global config directories, respecting "enabled": false.
• SessionStart (before_agent_start/2): Runs startup hooks once and injects systemMessage steps.
• PreInvocation (before_request/2): Runs before model invocation and injects transient ephemeralMessage or userMessage steps into derived.messages for that turn.
• PreToolUse (before_tool/3): Matches tool names against matcher ("*", "", or regex), sends camelCase JSON payload on stdin, and parses stdout JSON (decision: "allow" | "deny" | "ask" | "force_ask" and shallow top-level overwrite map).
• PostToolUse (after_tool/4): Runs matching post-tool commands with error metadata when a tool fails.
• PostInvocation (after_tools/2): Supports terminationBehavior: "force_continue".
• Stop (after_run/2): Sends terminationReason: "NO_TOOL_CALL" and honors decision: "continue" + reason.