fix: load the same config from_pretrained and get_sae_config

[chanind]

Description

This PR unifies the code path for from_pretrained and get_sae_config so the config dict should match, and adds a test asserting this for a jbloom/gpt2 SAE.

Fixes #351

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] This change requires a documentation update

Checklist:

• [x] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] I have added tests that prove my fix is effective or that my feature works
• [x] New and existing unit tests pass locally with my changes
• [x] I have not rewritten tests relating to key interfaces which would affect backward compatibility

You have tested formatting, typing and unit tests (acceptance tests not currently in use)

• [x] I have run make check-ci to check format and linting. (you can run make format to format code if needed.)

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 66.14%. Comparing base (b8703fe) to head (18143b7). Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sae_lens/toolkit/pretrained_sae_loaders.py	80.00%	1 Missing and 2 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #361 +/- ## ========================================== - Coverage 66.17% 66.14% -0.03% ========================================== Files 25 25 Lines 3367 3373 +6 Branches 429 432 +3 ========================================== + Hits 2228 2231 +3 - Misses 1020 1021 +1 - Partials 119 121 +2 ```

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[chanind]

I noticed that as well - it looks like the neuronpedia_id property is only set on the config in the SAE, but not in the config_dict that gets returned from SAE.from_pretrained(). I'm not sure what the reason for that is, or if it's simply an oversight. I can add it to the the config_dict so it's set every if that makes more sense. I'm also not sure what the idea with the neuronpedia property is

[chanind]

I updated the PR to include neuronpedia_id in the config in both places. I think the neuronpedia properly was likely just a typo, since there's no equivalent property on the SAEConfig class.