The hook system — register handlers for lifecycle events, fire them in-process, or drive them from config

Notes & tips

• def handler(**context). The single most common mistake is a positional context parameter.
• fire_sync for synchronous code. fire / execute are async.
• HookEvent values are the Claude Code names. One enum spans the in-process and Claude Code contracts.
• Declarative vs imperative. HookConfig/from_yaml for config; HookRegistry for embedded Python.