find symbols and protocols

now that, in the `I4kFindSymbols`, `!&+#` have the same level, and function (it seems) as the new "protocol symbols" (they all end up by a `:`, as the `new URL(window.location).protocol` has), `gopher:`, `git:`, `finger:` etc.

- how should they handle a "Find query"? `new URL()` might not give detail on the URI parsing
- by default we're in a web browser (first used case), and trying to resolve the user request, even though the browser does not support this (but some remote/local web-URL might be able to proxy them for us, if we build the proxy_app + protocol path correctly)

```txt
gemini:hello world
gemini: hello world
gemini: hello world
gemini:!d hello world
gemini:!m tokyo
gemini:+capsule hello world
gemini:&network username capsule-id
gemini://my-gemini-capsule.example.org/some/path
```
Or more generally (pseudo https://en.wikipedia.org/wiki/Web_Ontology_Language)
```txt
other-protocol://
other-protocol:[<;symbol><;engine>]%20[query]
```

Start by tracing I4kFindSymbols and how the browser URL object handles protocol schemes. Compare the listed gemini:, gopher:, git:, and finger: forms, then define how Find queries and URI parsing should work for each; done means the behavior is specified for the examples and unsupported browser protocols have a clear resolution path.

Written by the indexing model from the issue text.