Default Workflow seems like a bit of a hand grenade for juniors

preface: I had a little look into the history of the default workflow after writing this issue and why it came about through the issues, so I sort of understand if there's reluctance to go back to screenshot commit and diff testing rather than this git workflow, possibly what I want isn't right for the project (in which case I might tend towards a fork). Close this if you think it's not applicable, but I need to get it off my mind as it's my main roadblock in bringing huxley as a core piece of my front-end workflow right now. The search for a good screenshot regression testing workflow continues I guess.

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Hey there, this might seem a bit critical but it's only because huxley is, for me, so close yet just a little too cumbersome for use in a design heavy project where I'd like to screenshot every design component, possibly with a number of permutations.

The main problem for me is the default workflow, which is enough of a hand grenade for juniors that if it messes up their repository state, they can get confused about the correct steps to recover their work. I really believe the only tools that should mess with git should be version control tools, which this isn't, and I shouldn't have juniors thinking twice about running huxley because their repo wasn't in the right state. IMO the default should instead be something completely non-destructive, I'd think the best default would be a simple fill in the gaps approach where:

if there are tests without a recorded set of actions or screenshots missing, the CLI lists them out and then asks if you'd like to fill them out:

```
$ hux project/Huxleyfile.json

The following tests are missing recordings or screenshots:
InputLockup
SearchPanel
WidgetList

Do you wish to record and write screenshots for them now [Y/n]
```

...and if the recordings and screenshots ARE in place, runs through the lot with a less verbose output, grouped by Huxleyfiles, ie:

```
$ hux project/Huxleyfile.json

./project/Huxleyfile.json
InputLockup 1 ✔ 2 ✔
SearchPanel 1 ✔ 2 ✔ 3 ✔
WidgetList 1 ❌ diff at project/Huxleyfile/WidgetList.hux/firefox-1-diff.png
```

The only other thing I'd potentially want here would be an 'update' mode, where you can run through the entire set of tests, and if the test fails, have a chance to look at the result and see whether you want to replace the existing screenshots or not.

Start at the CLI entry point that handles a Huxleyfile and trace the current default workflow for recordings, screenshots, and git state. Compare that behavior with the proposed missing-test listing, fill-in flow, grouped results, and optional update mode; done means the workflow is non-destructive and clearly reports or updates the requested artifacts.

Written by the indexing model from the issue text.