Add workflow to prevent accidentally merging fixup commits

[jonathan-conder]

Description

I messed this up recently (canonical/sdkcraft#167) and don't think I can rely on remembering to do it every time.

Self-review quick check

• Make decisions that cost a lot to reverse explicit in the PR description.
• Avoid nested conditions.
• Delete dead code and redundant comments.
• Normalise symmetries by sticking to doing identical things identically.

// one way to handle errors
if err := f(); err != nil {
   ...
}

// one way to handle multiple returns
val, err := f()
if err != nil {
   ...
}
...

• Check that coupled code elements, files, and directories are adjacent. For example, test data is stored as close as possible to a test.
• Put variable declaration and initialisation together.
• Divide large expressions into digestable and self-explanatory ones. Use multiple variables if required.
• Put a blank line between two logically different chunks of code.
• Follow the style guide for new error messages.

Docs

• I have checked and added or updated relevant documentation.
• I have checked and added or updated relevant release notes.
• I have included the technical author in the review.

Or:

• I confirm the PR has no implications for documentation.

[github-actions]

TICS Quality Gate

❌ Failed

The following errors have occurred during analysis:

❌ [ERROR 5333] Project database 'workshop' already is connected to a started TICSQServer process that has not registered a stop time. To avoid data corruption, analysis is aborted. Details of the other TICSQServer process: started at 2025-08-14 03:36:53.000 by user ubuntu.

Automatic-tests / code-coverage / TICS GitHub Action

[github-actions]

TICS Quality Gate

❌ Failed

The following errors have occurred during analysis:

❌ [ERROR 5333] Project database 'workshop' already is connected to a started TICSQServer process that has not registered a stop time. To avoid data corruption, analysis is aborted. Details of the other TICSQServer process: started at 2025-08-14 03:36:53.000 by user ubuntu.

Automatic-tests / code-coverage / TICS GitHub Action