Dont use require() for imports in TS files (#1665)

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> [!IMPORTANT]
> Replace `require()` with `import` for `ThrowIfVersionMismatch` in
TypeScript files and update comments for upgrade guidance.
> 
>   - **Imports**:
> - Replace `require()` with `import` for `ThrowIfVersionMismatch` in
`index.ts.j2`, `react/baml_client/index.ts`, and
`typescript/baml_client/index.ts`.
>   - **Error Handling**:
> - Remove error handling for `require()` failures, as `import` will
handle this.
>   - **Comments**:
> - Add comments in all files to guide users on upgrading
`@boundaryml/baml` if import fails.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
src="https://img.shields.io/badge/Ellipsis-blue?color=175173">](https://www.ellipsis.dev?ref=BoundaryML%2Fbaml&utm_source=github&utm_medium=referral)<sup>
for 295be65. It will automatically
update as commits are pushed.</sup>

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Author: aaronvg

engine/language_client_codegen/src/typescript/templates/index.ts.j2

@@ -1,34 +1,23 @@
-export const version = "{{ version }}";
-
+/**
+ * If this import fails, you may need to upgrade @boundaryml/baml.
+ * 
+ * Please upgrade @boundaryml/baml to {{version}}.
+ * 
+ * $ npm install @boundaryml/baml@{{version}}
+ * $ yarn add @boundaryml/baml@{{version}}
+ * $ pnpm add @boundaryml/baml@{{version}}
+ * 
+ * If nothing else works, please ask for help:
+ * 
+ * https://github.com/boundaryml/baml/issues
+ * https://boundaryml.com/discord
+ * 
+ **/
+import { ThrowIfVersionMismatch } from "@boundaryml/baml";
 
-let ThrowIfVersionMismatch: (version: string) => void;
-try {
-  ThrowIfVersionMismatch = require("@boundaryml/baml").ThrowIfVersionMismatch;
-} catch (error) {
-  
-}
+export const version = "{{ version }}";
 
-if (ThrowIfVersionMismatch) {
-  ThrowIfVersionMismatch(version);
-} else {
-  // You're probably using a different version of baml.
-  // Please upgrade to the version used by generators.baml.
-  const errorMessage = `Update to @boundaryml/baml required.
-  Version of index.ts.j2 (see generators.baml): ${version}
-  
-  Please upgrade @boundaryml/baml to ${version}.
-  
-  $ npm install @boundaryml/baml@${version}
-  $ yarn add @boundaryml/baml@${version}
-  $ pnpm add @boundaryml/baml@${version}
-  
-  If nothing else works, please ask for help:
-  
-  https://github.com/boundaryml/baml/issues
-  https://boundaryml.com/discord`;
-  
-  throw new Error(errorMessage.trim());
-}
+ThrowIfVersionMismatch(version);
 
 
 {% if default_client_mode == GeneratorDefaultClientMode::Async %}