feat: add script-file input for lint-friendly external JS scripts

Closes #714

Inline `script` is a YAML string — invisible to linters and IDEs.
The common workaround was wrapping a `require` call inside the inline script,
which still needs boilerplate and assumes a path convention.

New optional `script-file` input that accepts a path to a JS file.
The file must `module.exports` an async function receiving the standard
IoC dependency bag (`github`, `octokit`, `getOctokit`, `context`, `core`,
`exec`, `glob`, `io`, `require`).

```yaml
- uses: actions/checkout@v4
- uses: actions/github-script@v9
  with:
    script-file: .github/scripts/my-script.js
```

`script` and `script-file` are mutually exclusive — exactly one must be provided.
Relative paths resolve against `$GITHUB_WORKSPACE`; absolute paths are used as-is.

- `action.yml` — adds `script-file` input; makes `script` optional
- `src/script-file.ts` — path resolution and script loading logic
- `src/args.ts` — `AsyncFunctionArguments` extracted from `async-function.ts` so neither execution path depends on the other
- `src/main.ts` — mutual-exclusion validation; dispatches to the right execution path
- `types/non-webpack-require.ts` — corrects `__non_webpack_require__` type from deprecated `NodeRequire` / wrong `NodeJS.RequireResolve` to `NodeJS.Require`
- `__test__/script-file.test.ts` — 10 tests covering path resolution, arg forwarding, error cases
- `README.md` — new `## Script file` section with usage, IoC bag table, path resolution rules
- `.github/fixtures/script-file/` — fixture JS files for integration tests
- `.github/workflows/integration.yml` — 10 new integration test jobs: happy path (relative path, absolute path, all IoC args, json/string encoding,
  require-in-file) and error cases (both inputs set, neither set, nonexistent file, non-function export, file:// protocol)

src/args.ts

@@ -0,0 +1,18 @@
+import * as core from '@actions/core'
+import * as exec from '@actions/exec'
+import type {context, getOctokit} from '@actions/github'
+import * as glob from '@actions/glob'
+import * as io from '@actions/io'
+
+export type AsyncFunctionArguments = {
+  context: typeof context
+  core: typeof core
+  github: ReturnType<typeof getOctokit>
+  octokit: ReturnType<typeof getOctokit>
+  getOctokit: typeof getOctokit
+  exec: typeof exec
+  glob: typeof glob
+  io: typeof io
+  require: NodeJS.Require
+  __original_require__: NodeJS.Require
+}

src/async-function.ts

@@ -1,24 +1,8 @@
-import * as core from '@actions/core'
-import * as exec from '@actions/exec'
-import type {context, getOctokit} from '@actions/github'
-import * as glob from '@actions/glob'
-import * as io from '@actions/io'
+import type {AsyncFunctionArguments} from './args'
+export type {AsyncFunctionArguments}
 
 const AsyncFunction = Object.getPrototypeOf(async () => null).constructor
 
-export declare type AsyncFunctionArguments = {
-  context: typeof context
-  core: typeof core
-  github: ReturnType<typeof getOctokit>
-  octokit: ReturnType<typeof getOctokit>
-  getOctokit: typeof getOctokit
-  exec: typeof exec
-  glob: typeof glob
-  io: typeof io
-  require: NodeRequire
-  __original_require__: NodeRequire
-}
-
 export function callAsyncFunction<T>(
   args: AsyncFunctionArguments,
   source: string

src/main.ts

@@ -10,6 +10,7 @@ import {RequestRequestOptions} from '@octokit/types'
 import {callAsyncFunction} from './async-function'
 import {createConfiguredGetOctokit} from './create-configured-getoctokit'
 import {RetryOptions, getRetryOptions, parseNumberArray} from './retry-options'
+import {callScriptFile} from './script-file'
 import {wrapRequire} from './wrap-require'
 
 process.on('unhandledRejection', handleError)
@@ -58,7 +59,17 @@ async function main(): Promise<void> {
   }
 
   const github = getOctokit(token, opts, retry, requestLog)
-  const script = core.getInput('script', {required: true})
+  const scriptInline = core.getInput('script')
+  const scriptFile = core.getInput('script-file')
+
+  if (scriptInline && scriptFile) {
+    throw new Error(
+      'Only one of "script" or "script-file" may be provided, not both'
+    )
+  }
+  if (!scriptInline && !scriptFile) {
+    throw new Error('One of "script" or "script-file" must be provided')
+  }
 
   // Wrap getOctokit so secondary clients inherit retry, logging,
   // orchestration ID, and the action's retries input.
@@ -71,21 +82,22 @@ async function main(): Promise<void> {
   )
 
   // Using property/value shorthand on `require` (e.g. `{require}`) causes compilation errors.
-  const result = await callAsyncFunction(
-    {
-      require: wrapRequire,
-      __original_require__: __non_webpack_require__,
-      github,
-      octokit: github,
-      getOctokit: configuredGetOctokit,
-      context,
-      core,
-      exec,
-      glob,
-      io
-    },
-    script
-  )
+  const args = {
+    require: wrapRequire,
+    __original_require__: __non_webpack_require__,
+    github,
+    octokit: github,
+    getOctokit: configuredGetOctokit,
+    context,
+    core,
+    exec,
+    glob,
+    io
+  }
+
+  const result = scriptFile
+    ? await callScriptFile(args, scriptFile, __non_webpack_require__)
+    : await callAsyncFunction(args, scriptInline)
 
   let encoding = core.getInput('result-encoding')
   encoding = encoding ? encoding : 'json'

src/script-file.ts

@@ -0,0 +1,29 @@
+import * as path from 'path'
+import type {AsyncFunctionArguments} from './args'
+
+export function resolveScriptFilePath(scriptFile: string): string {
+  if (scriptFile.startsWith('file://')) {
+    throw new Error('"script-file" must not use the "file://" protocol')
+  }
+
+  return path.isAbsolute(scriptFile)
+    ? scriptFile
+    : path.resolve(process.env['GITHUB_WORKSPACE']!, scriptFile)
+}
+
+export async function callScriptFile(
+  args: AsyncFunctionArguments,
+  scriptFile: string,
+  requireFn: NodeJS.Require
+): Promise<unknown> {
+  const resolvedPath = resolveScriptFilePath(scriptFile)
+  const scriptFn = requireFn(resolvedPath)
+
+  if (typeof scriptFn !== 'function') {
+    throw new Error(
+      `"script-file" must export a function, got ${typeof scriptFn}`
+    )
+  }
+
+  return scriptFn(args)
+}