docs: add docs for tasks Result

src/content/docs/docs/guides/writing-tasks.mdx

@@ -117,4 +117,42 @@ If you're developing a plugin, you must use `setAction()` with lazy-loaded modul
 
 To learn more about how task actions are loaded, see the [Task Actions' lifecycle](/docs/plugin-development/explanations/lifecycle#task-actions-lifecycle) documentation.
 
+## Returning a result
+
+Task actions can optionally return a `Result` to signal success or failure to the CLI. When a task action returns a failed result, the CLI sets the process exit code to 1. This is useful when you want to indicate failure to scripts or CI pipelines without throwing an exception.
+
+To use this, import the `Result` type from `hardhat/types/utils` and the helper functions from `hardhat/utils/result`:
+
+```ts
+// tasks/accounts.ts
+import type { HardhatRuntimeEnvironment } from "hardhat/types/hre";
+import type { Result } from "hardhat/types/utils";
+import { successfulResult, errorResult } from "hardhat/utils/result";
+
+interface AccountTaskArguments {}
+
+export default async function (
+  _taskArguments: AccountTaskArguments,
+  hre: HardhatRuntimeEnvironment,
+): Promise<Result<string[], string>> {
+  const { provider } = await hre.network.connect();
+  const accounts = await provider.request({ method: "eth_accounts" });
+
+  if (accounts.length === 0) {
+    return errorResult("No accounts found");
+  }
+
+  return successfulResult(accounts);
+}
+```
+
+`Result<ValueT, ErrorT>` is a discriminated union:
+
+- `{ success: true; value: ValueT }` - a successful result, carrying a value
+- `{ success: false; error: ErrorT }` - a failed result, carrying error information
+
+Use `successfulResult(value?)` and `errorResult(error?)` to create these objects. Both helpers can be called without a parameter, in which case they set `value` or `error` to `undefined`.
+
+If a task action doesn't return a `Result` (for example, it returns `undefined` or any other value), the CLI exit code is left unchanged.
+
 {/* To learn more about tasks, please read [this guide](../advanced/create-task). */}

src/content/docs/docs/plugin-development/explanations/lifecycle.mdx

@@ -259,6 +259,12 @@ Inline actions are loaded immediately when the configuration file is evaluated,
 Plugins cannot use `setInlineAction()`. Attempting to do so will result in an error. Plugins must always use `setAction()` with lazy-loaded modules.
 :::
 
+### Returning a result
+
+The task action, either the inline callback you pass to `setInlineAction()`, or the `default` export of the module loaded via `setAction()`, can optionally return a `Result` value. If the action returns a result with `success: false`, the CLI sets the process exit code to 1.
+
+To learn more, see the [Returning a result](/docs/guides/writing-tasks#returning-a-result) section of the Writing Hardhat tasks guide.
+
 ## Configuration Variables' lifecycle
 
 There are two things that plugins can do with Configuration Variables: