chore(ffi-linkage): add MIT license to vscode extension

LICENSE file (MIT, © 2025 agra — matching the repo-root LICENSE) +
`license: "MIT"` manifest field + README license section. Clears vsce's
missing-license warning; rebuilt the vsix.

editors/vscode/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2025 agra
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+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.

editors/vscode/README.md

@@ -22,4 +22,4 @@ The `sx` compiler must be installed and on your `PATH` (or point the extension a
 
 ## License
 
-See the repository for license details.
+[MIT](LICENSE) © agra

editors/vscode/package.json

@@ -23,6 +23,7 @@
   "categories": [
     "Programming Languages"
   ],
+  "license": "MIT",
   "activationEvents": [
     "onLanguage:sx"
   ],