Add hooks system with pi.send() for external message injection

- Hook discovery from ~/.pi/agent/hooks/, .pi/hooks/, --hook flag
- Events: session_start, session_switch, agent_start/end, turn_start/end, tool_call, tool_result, branch
- tool_call can block execution, tool_result can modify results
- pi.send(text, attachments?) to inject messages from external sources
- UI primitives: ctx.ui.select/confirm/input/notify
- Context: ctx.exec(), ctx.cwd, ctx.sessionFile, ctx.hasUI
- Docs shipped with npm package and binary builds
- System prompt references docs folder

packages/coding-agent/src/core/hooks/index.ts

@@ -1,5 +1,6 @@
-export { type LoadedHook, type LoadHooksResult, loadHooks } from "./loader.js";
+export { discoverAndLoadHooks, type LoadedHook, type LoadHooksResult, loadHooks, type SendHandler } from "./loader.js";
 export { type HookErrorListener, HookRunner } from "./runner.js";
+export { wrapToolsWithHooks, wrapToolWithHooks } from "./tool-wrapper.js";
 export type {
 	AgentEndEvent,
 	AgentStartEvent,
@@ -12,6 +13,12 @@ export type {
 	HookEventContext,
 	HookFactory,
 	HookUIContext,
+	SessionStartEvent,
+	SessionSwitchEvent,
+	ToolCallEvent,
+	ToolCallEventResult,
+	ToolResultEvent,
+	ToolResultEventResult,
 	TurnEndEvent,
 	TurnStartEvent,
 } from "./types.js";