Enforce strict project structure for Noir compilation

[hsy822]

Problem

The previous compilation logic used a flexible search to locate Nargo.toml and determine the project root.
This could lead to unintended behavior, such as:

• Zipping the entire workspace
• Selecting the wrong directory for compilation
• Errors when users did not follow a standard project structure

Solution

This PR modifies the logic to enforce a strict, conventional Noir project structure.

• A .nr file must be located inside a src folder
• A Nargo.toml file must exist in the parent directory of the src folder (the project root)
• If these conditions are not met, the compilation process is aborted
• A clear error message is shown to the user, guiding them to set up their project correctly

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How to Test

Follow these steps to verify the new compilation logic:

1. Create a project folder
   In your workspace, create a new folder named after your project (e.g., hello_noir).

2. Create a src directory
   Inside the project folder, create a subfolder named src.

3. Add a source file
   Inside src, create a file named main.nr and add the following content:

   fn main(x: Field, y: pub Field) {
       assert(x != y);
   }

4. Add a project configuration file
   In the project root (the same level as src), create a file named Nargo.toml and add the following content:

   [package]
   name = "hello_noir"
   type = "bin"
   authors = [""]

5. Compile the project
   Open the main.nr file in the editor, then click Compile in the Noir compiler.

6. Check the build output
   If the compilation succeeds, a new folder named build should appear inside your project directory.
   The folder should contain:

   • program.json
   • prover.toml

If both files are generated, the test is successful.

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[ioedeveloper]

I get the error in the image below for a valid project structure.

[hsy822]

I get the error in the image below for a valid project structure.

The project root detection logic has been updated to provide greater flexibility.

Previously, the compiler only supported projects nested within a dedicated folder (e.g., (workspace)/project/src). This commit enhances the logic to also handle projects located directly at the workspace root (e.g., (workspace)/src).

Both of the following structures are now correctly identified and supported:

• (workspace)/project/src/...
• (workspace)/src/...