add-license-header

name	add-license-header
description	Add the project's canonical SPDX license header to source files that are missing one. Use when asked to add a license header to a file or directory, e.g. "add the license header to src/foo.ts" or "make sure every file in src/ has our license header."

1. Determine target files. From the user's request, resolve the set of files to process -- either a single path or every source file under a given directory.

2. Check each file for an existing header. Read the first 20 lines of each target file and look for the string SPDX-License-Identifier.

3. Skip files that already have a header. If SPDX-License-Identifier appears in the first 20 lines, do not touch that file. Never add a second header to a file that already has one.

4. Insert the header at the very top. For files that lack a header, insert these exact two lines as the first two lines of the file, above all existing content (including shebangs, comments, or blank lines):

   // SPDX-License-Identifier: Apache-2.0
   // Copyright (c) 2026 Acme Corp
   

   The header must always be the very first thing in the file -- never insert it after existing content.

5. Report results. List which files were changed and which were skipped (already had a header).