feat: add trademark notices and legal disclaimers to README and create NOTICE file

Author: vchan-in

NOTICES.md

@@ -0,0 +1,28 @@
+# Third-Party Trademark Notices
+
+## Trademarks
+
+The following trademarks belong to their respective owners. Their use in this
+project is solely to identify the third-party services with which HackLM Migrate
+is designed to interoperate (nominative fair use). HackLM makes no claim of
+ownership over any of these marks.
+
+| Mark | Owner |
+|------|-------|
+| ChatGPT™, OpenAI™ | OpenAI, Inc. |
+| Claude™ | Anthropic, PBC |
+| Google Gemini™, Google DeepMind™ | Google LLC |
+| Grok™ | xAI Corp and/or X Corp |
+| Perplexity™ | Perplexity AI, Inc. |
+
+All trademarks are the property of their respective owners.
+
+## Non-Affiliation
+
+HackLM Migrate is an independent, community-driven open-source project.  
+It is **not** affiliated with, endorsed by, or sponsored by OpenAI, Anthropic,
+Google, xAI, X Corp, Perplexity AI, or any other AI provider whose services
+this software is designed to work with.
+
+Use of these names does not imply any relationship, partnership, or approval
+between HackLM and the trademark owners.

README.md

@@ -75,6 +75,14 @@ Contributions are welcome. Please read [CONTRIBUTING.md](CONTRIBUTING.md) before
 - [Architecture Decision Records](https://migrate.hacklm.dev/decisions/) — every major design choice documented
 - [Roadmap](https://migrate.hacklm.dev/roadmap/) — planned work and open contribution areas
 
+## Legal
+
+ChatGPT™ and OpenAI™ are trademarks of OpenAI, Inc. Claude™ is a trademark of Anthropic, PBC. Google Gemini™ and Google DeepMind™ are trademarks of Google LLC. Grok™ is a trademark of xAI Corp and/or X Corp. Perplexity™ is a trademark of Perplexity AI, Inc. All trademarks are the property of their respective owners and are used here solely to identify the third-party services with which HackLM Migrate is designed to interoperate.
+
+HackLM Migrate is an independent, community-driven open-source project. It is not affiliated with, endorsed by, or sponsored by OpenAI, Anthropic, Google, xAI, X Corp, Perplexity AI, or any other AI provider whose services this software is designed to work with.
+
+See [NOTICES.md](NOTICES.md) for the full trademark attribution table.
+
 ## License
 
 GNU General Public License v3.0 — see [LICENSE](LICENSE).