feat(coding-agent): type ToolCallEvent.input per tool

Matches ToolResultEvent pattern with typed inputs via discriminated union.

- Export *ToolInput types from tool schemas
- Add *ToolCallEvent interfaces for each built-in tool
- Add isToolCallEventType() guard with overloads for built-ins

Direct narrowing (event.toolName === "bash") doesn't work due to
CustomToolCallEvent.toolName: string overlapping with literals.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/coding-agent/src/core/tools/edit.ts

@@ -1,5 +1,5 @@
 import type { AgentTool } from "@mariozechner/pi-agent-core";
-import { Type } from "@sinclair/typebox";
+import { type Static, Type } from "@sinclair/typebox";
 import { constants } from "fs";
 import { access as fsAccess, readFile as fsReadFile, writeFile as fsWriteFile } from "fs/promises";
 import {
@@ -19,6 +19,8 @@ const editSchema = Type.Object({
 	newText: Type.String({ description: "New text to replace the old text with" }),
 });
 
+export type EditToolInput = Static<typeof editSchema>;
+
 export interface EditToolDetails {
 	/** Unified diff of the changes made */
 	diff: string;