Adding ability to utilize different git compatible/local folder as unique namespace for sdrf yaml template

Adding ability to utilize specific "namespace" as source of the yaml. This would be specifically powerful for organization and development of yaml onward. Example use case can be

```
name: human
namespace: github.com/bigbio/phosphoproteomics-sdrf-template
extends: minimum
```

If the resource is a `git` compatible resource, it will first look into `github.com/bigbio/phosphoproteomics-sdrf-template`, load all yaml at root and identify the `minimum` template to extend. We can also have it automatically detect namespace to extend.

```
name: human
extends: github.com/bigbio/phosphoproteomics-sdrf-template/minimum
```

The above would perform the same but we do not have to specify a separate namespace. This feature would make independent yaml development a lot easier as well as keeping template name simple.

Start by tracing how the YAML namespace and extends fields are currently loaded and resolved, then inspect the template-loading entry point. Define behavior for git-compatible and local sources, root YAML discovery, and explicit versus automatic namespace detection. Done means both examples resolve the minimum template consistently, with coverage for local and git-compatible resources.

Written by the indexing model from the issue text.