Use posix separators for convex.config (#41957)

Fixes an error with separators in windows vs. unix:
```Error: ROR] Could not resolve "./convex\\convex.config.js"

  ✖ esbuild failed: Error: Build failed with 1 error:
  error: Could not resolve "./convex\\convex.config.js"
```

We have to use `\` instead of`/` sometimes in the definition path.

GitOrigin-RevId: 1457a5170c8a52784f828bffd2b82a91bbf7dd7c

Author: jordanhunt22

src/cli/lib/components/definition/directoryStructure.ts

@@ -53,7 +53,10 @@ export function qualifiedDefinitionPath(
   workingDir = ".",
 ) {
   const definitionPath = path.relative(workingDir, directory.definitionPath);
-  return `./${definitionPath}`;
+  const posixDefinitionPath = definitionPath
+    .split(path.sep)
+    .join(path.posix.sep);
+  return `./${posixDefinitionPath}`;
 }
 
 // NB: The process cwd will be used to resolve the directory specified in the constructor.