refactor(prompt-templates): migrated prompt utilities to pi-utils package

- Extracted prompt rendering and formatting utilities from coding-agent to centralized pi-utils package with new API surface (prompt.render, prompt.format, prompt.registerHelper).
- Migrated parseFrontmatter utility from coding-agent to pi-utils package; updated 8 files to import from @oh-my-pi/pi-utils.
- Removed 170-line prompt-format.ts module and consolidated 192 lines of Handlebars helper registrations into pi-utils prompt module.
- Updated 60+ files across coding-agent and typescript-edit-benchmark to use new prompt.render() and prompt.format() API from pi-utils.
- Simplified prompt-templates.ts by delegating core functionality to pi-utils while retaining custom helper registrations (jtdToTypeScript, jsonStringify, etc.).

packages/coding-agent/src/tools/python.ts

@@ -4,9 +4,8 @@ import type { AgentTool, AgentToolContext, AgentToolResult, AgentToolUpdateCallb
 import type { ImageContent } from "@oh-my-pi/pi-ai";
 import type { Component } from "@oh-my-pi/pi-tui";
 import { Markdown, Text } from "@oh-my-pi/pi-tui";
-import { getProjectDir } from "@oh-my-pi/pi-utils";
+import { getProjectDir, prompt } from "@oh-my-pi/pi-utils";
 import { type Static, Type } from "@sinclair/typebox";
-import { renderPromptTemplate } from "../config/prompt-templates";
 import type { RenderResultOptions } from "../extensibility/custom-tools/types";
 import { executePython, getPreludeDocs, type PythonExecutorOptions } from "../ipy/executor";
 import type { PreludeHelper, PythonStatusEvent } from "../ipy/kernel";
@@ -136,7 +135,7 @@ function renderJsonTree(value: unknown, theme: Theme, expanded: boolean, maxDept
 export function getPythonToolDescription(): string {
 	const helpers = getPreludeDocs();
 	const categories = groupPreludeHelpers(helpers);
-	return renderPromptTemplate(pythonDescription, { categories });
+	return prompt.render(pythonDescription, { categories });
 }
 
 export interface PythonToolOptions {