feature: Github OAuth button placeholder

[Cragsmann]

Summary

• Add disabled "Sign in with GitHub" OAuth button with "Coming soon" tooltip to the PAT modal
• Add "or" divider between OAuth button and PAT input using PF6 Flex layout
• Move PAT helper text into FormHelperText component (PF6 pattern)

Implements SRVOCF-862

Screenshots

Test plan

• OAuth button renders as disabled with aria-disabled="true"
• "Coming soon" tooltip appears on hover
• "or" divider separates OAuth button from PAT input
• PAT form still works (enter token, connect, error handling)
• Existing unit tests pass (14/14)

[twoGiants]

Reviewing your first contribution 😸 👍

Add a unit test -> button is there but not clickable so no action is possible.

[Cragsmann]

Reviewing your first contribution 😸 👍

Add a unit test -> button is there but not clickable so no action is possible.

thanks for review, As task description says: 'Button placeholder" I thought such test would have meaning after OAuth is completed and button functional.

[twoGiants]

Reviewing your first contribution 😸 👍
Add a unit test -> button is there but not clickable so no action is possible.

thanks for review, As task description says: 'Button placeholder" I thought such test would have meaning after OAuth is completed and button functional.

It has meaning now too for the case that the button is removed (by accident) the test will let us know.

[twoGiants]

Two more things.

1. Can you get familiar with the process? Ask Matej about it.

   Each "feature" implementation needs an entry for Claude in features.json and claude-progress.json.

   We use those to init claude in a working session so that he knows what was done.

2. Please remove the link to Jira from the description. I wouldn't link in public Github to our internal Jira tickets.