Clean up code. Reorganize files. Port stuff from other branches. + more

This turns the project into a monorepo using pnpm workspaces,
dramatically simplifying the build process. It also fixes a lot of bugs
and just generally makes the codebase a lot cleaner.

package.json

@@ -0,0 +1,17 @@
+{
+    "name": "impost-monorepo",
+    "version": "0.0.0",
+    "private": true,
+    "scripts": {
+        "build": "pnpm build:all",
+        "build:all": "pnpm build:solver && pnpm build:lib && pnpm build:widget",
+        "build:solver": "pnpm --filter solver build",
+        "build:lib": "pnpm --filter lib build",
+        "build:widget": "pnpm --filter widget build",
+        "dev:example": "pnpm --filter example-app dev"
+    },
+    "devDependencies": {
+        "typescript": "^5.0.0"
+    },
+    "packageManager": "pnpm@10.21.0+sha512.da3337267e400fdd3d479a6c68079ac6db01d8ca4f67572083e722775a796788a7a9956613749e000fac20d424b594f7a791a5f4e2e13581c5ef947f26968a40"
+}