fix(license): keep LICENSE to standard MIT text so it is detected as MIT

Move the attribution notice out of LICENSE into ATTRIBUTION.md. The appended
notice dropped the file below GitHub's license-match threshold, so it showed as
Other/NOASSERTION instead of MIT, which blocks dependency adoption.

ATTRIBUTION.md

@@ -16,7 +16,8 @@ Yams and libyaml source remain available from their upstream projects:
 - https://github.com/jpsim/Yams
 - https://pyyaml.org/wiki/LibYAML
 
-The license file includes a matching attribution notice.
+This file is the canonical attribution notice for the project; the `LICENSE`
+file is kept to the standard MIT text so it is correctly detected as MIT.
 
 The private `PureYAMLResearch` repository contains a full Yams source snapshot
 for study and compatibility research. That repository is not the implementation

LICENSE

@@ -19,19 +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.
-
-Attribution Notice
-------------------
-
-PureYAML is an independent Swift implementation. It is informed by the behavior
-and public API surface of Yams, and by the YAML parsing model embodied in Yams'
-bundled CYaml / libyaml-derived C sources.
-
-PureYAML does not copy Yams Swift source code, CYaml C source code, or libyaml C
-source code into this public package.
-
-Yams:
-https://github.com/jpsim/Yams
-
-libyaml:
-https://pyyaml.org/wiki/LibYAML