Search behavior on obo files not as expected

I noticed this first when going through the tutorials and running search via the cli:

```sh
runoak --input obolibrary:fbbt.obo search 'wing vein'
```

What is expected in the tutorial is:
```sh
FBbt:00004751 ! wing vein
FBbt:00004754 ! axillary vein
FBbt:00004759 ! wing vein L1
FBbt:00004760 ! wing vein L2
```

But what is returned by OAK is:

```sh
FBbt:00004751 ! wing vein
```

This behavior is seen on:
- `main` (ref `9bd64d9`)
- v0.1.19

After a bit of tinkering I realized that this might be because the default search behavior might have changed from `SearchTermSyntax.REGULAR_EXPRESSION` to `SearchTermSyntax.STARTS_WITH`.

Start by running the documented `runoak --input obolibrary:fbbt.obo search 'wing vein'` command and inspect the default handling of `SearchTermSyntax.REGULAR_EXPRESSION` versus `SearchTermSyntax.STARTS_WITH`. Compare the result with the four expected tutorial matches; done means the CLI returns those matches on main and v0.1.19 behavior is understood or corrected.

Written by the indexing model from the issue text.