Return a clear error for malformed tool ids in guid_to_repository

[SAY-5]

A TRS tool id whose decoded guid has fewer than four slashes (for example localhost/repos/owner) reaches guid_to_repository, where tool_id.split("/", 5) returns too few values to unpack. The bare ValueError: not enough values to unpack (expected 5, got 3) propagates out of the /api/ga4gh/trs/v2/tools/{id}/versions endpoint as a 500 instead of a request error. Fixes #23139.

This raises RequestParameterInvalidException for malformed ids so the API returns a 400, and reads the owner/name by index so a guid that still carries a trailing version segment keeps working.

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. [add testing steps and prerequisites here if you didn't write automated tests covering all your changes]

License

• I agree to license these and all my past contributions to the core galaxy codebase under the MIT license.

[SAY-5]

Pushed a fix for the mypy failure on the new test: it was passing app=None against the ToolShedApp-typed parameter. Since the malformed-id check runs before app is dereferenced, I cast None to ToolShedApp so the type checker is satisfied while still exercising the error path.

[mvdbeek]

The fix looks great but the test doesn't add a lot of value. Can you either remove the test or test the positive cases as well ?