feat: live LSP error underlines + improved VS Code extension

bux-lsp 0.17 publishes in-process diagnostics on open/change/save so
editors show red squiggles for lex/parse/type errors in the live buffer.
VS Code client discovers tools/bux-lsp, adds status bar/restart, richer
syntax/snippets, and docs (docs/LSP.md) for forum/editor setup.

vscode/tsconfig.json

@@ -2,12 +2,17 @@
     "compilerOptions": {
         "module": "commonjs",
         "target": "ES2020",
+        "lib": ["ES2020"],
         "outDir": "out",
         "rootDir": "src",
         "sourceMap": true,
         "strict": true,
-        "esModuleInterop": true
+        "esModuleInterop": true,
+        "skipLibCheck": true,
+        "forceConsistentCasingInFileNames": true,
+        "moduleResolution": "node",
+        "types": ["node", "vscode"]
     },
     "include": ["src"],
-    "exclude": ["node_modules", ".vscode-test"]
+    "exclude": ["node_modules", ".vscode-test", "out"]
 }