feat: migrate verified template implementation into main repo

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/capabilities/contracts.ts

@@ -0,0 +1,95 @@
+import { AppError } from "../lib/errors.js";
+
+export const EXAMPLE_ECHO_TOOL_NAME = "example.echo";
+export const EXAMPLE_SUMMARY_PROMPT_NAME = "example.summary";
+
+export type ExampleEchoToolInput = {
+  message: string;
+  uppercase?: boolean;
+};
+
+export type ExampleEchoToolResult = {
+  output: string;
+};
+
+export type ExampleSummaryPromptInput = {
+  topic: string;
+  audience?: string;
+};
+
+type ObjectRecord = Record<string, unknown>;
+
+function asRecord(value: unknown, context: string): ObjectRecord {
+  if (value && typeof value === "object" && !Array.isArray(value)) {
+    return value as ObjectRecord;
+  }
+
+  throw new AppError(`${context} must be an object`, "E_CONTRACT_INVALID_INPUT", {
+    cause: value,
+  });
+}
+
+function asNonEmptyString(value: unknown, field: string): string {
+  if (typeof value !== "string") {
+    throw new AppError(`${field} must be a string`, "E_CONTRACT_INVALID_INPUT", {
+      cause: value,
+    });
+  }
+
+  const normalized = value.trim();
+  if (!normalized) {
+    throw new AppError(`${field} must not be empty`, "E_CONTRACT_INVALID_INPUT", {
+      cause: value,
+    });
+  }
+
+  return normalized;
+}
+
+function asOptionalBoolean(value: unknown, field: string): boolean | undefined {
+  if (value === undefined) {
+    return undefined;
+  }
+
+  if (typeof value !== "boolean") {
+    throw new AppError(`${field} must be a boolean when provided`, "E_CONTRACT_INVALID_INPUT", {
+      cause: value,
+    });
+  }
+
+  return value;
+}
+
+export function parseExampleEchoToolInput(input: unknown): ExampleEchoToolInput {
+  const record = asRecord(input, EXAMPLE_ECHO_TOOL_NAME);
+
+  return {
+    message: asNonEmptyString(record.message, "message"),
+    uppercase: asOptionalBoolean(record.uppercase, "uppercase"),
+  };
+}
+
+export function runExampleEchoTool(input: unknown): ExampleEchoToolResult {
+  const parsed = parseExampleEchoToolInput(input);
+  return {
+    output: parsed.uppercase ? parsed.message.toUpperCase() : parsed.message,
+  };
+}
+
+export function parseExampleSummaryPromptInput(input: unknown): ExampleSummaryPromptInput {
+  const record = asRecord(input, EXAMPLE_SUMMARY_PROMPT_NAME);
+
+  return {
+    topic: asNonEmptyString(record.topic, "topic"),
+    audience:
+      record.audience === undefined
+        ? undefined
+        : asNonEmptyString(record.audience, "audience"),
+  };
+}
+
+export function renderExampleSummaryPrompt(input: unknown): string {
+  const parsed = parseExampleSummaryPromptInput(input);
+  const audienceLabel = parsed.audience ? ` for ${parsed.audience}` : "";
+  return `Write a concise summary about ${parsed.topic}${audienceLabel}.`;
+}