docs(license): keep LICENSE pure MIT so GitHub detects it; move attribution to NOTICE

GitHub's license API reported NOASSERTION (not MIT) for this repo: the derivative
and Microsoft-trademark paragraph appended after the MIT text pushed the file
below the detector's template-match threshold, so the repo carried no MIT label.

Split it the way upstream VS Code does — LICENSE is now verbatim MIT (the grant
and the copyright line are unchanged), and the Code-OSS provenance + trademark
disclaimer move to a dedicated NOTICE file. README's License section points at
both. Nothing is lost; MIT now detects.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ndemianc

LICENSE

@@ -19,12 +19,3 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
-
----
-
-LevelCode is a derivative of Code-OSS (https://github.com/microsoft/vscode),
-which is licensed under the MIT License, Copyright (c) Microsoft Corporation.
-LevelCode is not produced by, endorsed by, or affiliated with Microsoft.
-"Visual Studio Code" and related marks are trademarks of Microsoft.
-The upstream Code-OSS source is fetched at build time and is not redistributed
-in this repository.

NOTICE

@@ -0,0 +1,14 @@
+LevelCode
+=========
+
+LevelCode is licensed under the MIT License; see the LICENSE file.
+
+Third-party and derivative notices
+----------------------------------
+
+LevelCode is a derivative of Code-OSS (https://github.com/microsoft/vscode),
+which is licensed under the MIT License, Copyright (c) Microsoft Corporation.
+LevelCode is not produced by, endorsed by, or affiliated with Microsoft.
+"Visual Studio Code" and related marks are trademarks of Microsoft.
+The upstream Code-OSS source is fetched at build time and is not redistributed
+in this repository.

README.md

@@ -61,4 +61,4 @@ Code-OSS is MIT-licensed and free to fork, modify, and ship. LevelCode honors th
 
 ## License
 
-MIT — see [`LICENSE`](./LICENSE). A derivative of [Code-OSS](https://github.com/microsoft/vscode) (MIT, © Microsoft Corporation). Not affiliated with Microsoft.
+MIT — see [`LICENSE`](./LICENSE). A derivative of [Code-OSS](https://github.com/microsoft/vscode) (MIT, © Microsoft Corporation); see [`NOTICE`](./NOTICE) for attributions. Not affiliated with Microsoft.