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/read.ts

@@ -1,6 +1,6 @@
 import type { AgentTool } from "@mariozechner/pi-agent-core";
 import type { ImageContent, TextContent } from "@mariozechner/pi-ai";
-import { Type } from "@sinclair/typebox";
+import { type Static, Type } from "@sinclair/typebox";
 import { constants } from "fs";
 import { access as fsAccess, readFile as fsReadFile } from "fs/promises";
 import { formatDimensionNote, resizeImage } from "../../utils/image-resize.js";
@@ -14,6 +14,8 @@ const readSchema = Type.Object({
 	limit: Type.Optional(Type.Number({ description: "Maximum number of lines to read" })),
 });
 
+export type ReadToolInput = Static<typeof readSchema>;
+
 export interface ReadToolDetails {
 	truncation?: TruncationResult;
 }