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.

packages/widget/package-lock.json

@@ -8,6 +8,9 @@
             "name": "@impost/widget",
             "version": "0.1.0",
             "license": "BSL-1.0",
+            "dependencies": {
+                "comlink": "^4.4.2"
+            },
             "devDependencies": {
                 "@types/node": "^20.11.24",
                 "lit": "^3.1.2",
@@ -1433,7 +1436,6 @@
             "integrity": "sha512-ZsJzA5thDQMSQO788d7IocwwQbI8B5OPzmqNvpf3NY/+MHDAS759Wo0gd2WQeXYt5AAAQjzcrTVC6SKCuYgoCQ==",
             "dev": true,
             "license": "MIT",
-            "peer": true,
             "dependencies": {
                 "undici-types": "~6.21.0"
             }
@@ -1655,6 +1657,11 @@
             "dev": true,
             "license": "MIT"
         },
+        "node_modules/comlink": {
+            "version": "4.4.2",
+            "resolved": "https://registry.npmjs.org/comlink/-/comlink-4.4.2.tgz",
+            "integrity": "sha512-OxGdvBmJuNKSCMO4NTl1L47VRp6xn2wG4F/2hYzB6tiCb709otOxtEYCSvK80PtjODfXXZu8ds+Nw5kVCjqd2g=="
+        },
         "node_modules/compare-versions": {
             "version": "6.1.1",
             "resolved": "https://registry.npmjs.org/compare-versions/-/compare-versions-6.1.1.tgz",
@@ -2148,7 +2155,6 @@
             "integrity": "sha512-5gTmgEY/sqK6gFXLIsQNH19lWb4ebPDLA4SdLP7dsWkIXHWlG66oPuVvXSGFPppYZz8ZDZq0dYYrbHfBCVUb1Q==",
             "dev": true,
             "license": "MIT",
-            "peer": true,
             "engines": {
                 "node": ">=12"
             },
@@ -2422,7 +2428,6 @@
             "integrity": "sha512-jl1vZzPDinLr9eUt3J/t7V6FgNEw9QjvBPdysz9KfQDD41fQrC2Y4vKQdiaUpFT4bXlb1RHhLpp8wtm6M5TgSw==",
             "dev": true,
             "license": "Apache-2.0",
-            "peer": true,
             "bin": {
                 "tsc": "bin/tsc",
                 "tsserver": "bin/tsserver"
@@ -2461,7 +2466,6 @@
             "integrity": "sha512-BxAKBWmIbrDgrokdGZH1IgkIk/5mMHDreLDmCJ0qpyJaAteP8NvMhkwr/ZCQNqNH97bw/dANTE9PDzqwJghfMQ==",
             "dev": true,
             "license": "MIT",
-            "peer": true,
             "dependencies": {
                 "esbuild": "^0.25.0",
                 "fdir": "^6.5.0",