build(test): configure ts-jest to use correct tsconfig

I think *this* was why we were seeing weird flakiness around
default exports on CI

jest.config.js

@@ -1,6 +1,23 @@
-const {jest: jestConfig} = require('./src/config')
+const {
+  globals,
+  transformIgnorePatterns,
+  ...config
+} = require('./src/config/jest.config')
 
-module.exports = Object.assign(jestConfig, {
+/** @type{import('ts-jest/dist/types').InitialOptionsTsJest} */
+module.exports = {
+  ...config,
   roots: ['<rootDir>/src'],
   coverageThreshold: null,
-})
+  transformIgnorePatterns: [...transformIgnorePatterns, '.prettierrc.js'],
+  globals: {
+    'ts-jest': {
+      ...globals['ts-jest'],
+      tsconfig: './src/tsconfig.json',
+      diagnostics: {
+        warnOnly: true,
+        exclude: ['src/scripts/**/*.js', 'src/config/**/*.js'],
+      },
+    },
+  },
+}