Clear failure reasons

**Is your feature request related to a problem? Please describe.**

Our advice list is currently 395 lines long and `should-fail.txt` returns false. However, in certain scenarios in CI, devs would hit failures and they have a hard time understanding which of those advices contribute to the dep-analysis failure.

**Describe the solution you'd like**

Is there an easy way for the plugin to separate which advice is causing the failure? Maybe instead of
```
Advice for :library:powerscore
Unused dependencies which should be removed:
```

it would read:
```
Failure for :library:powerscore
Unused dependencies which should be removed:
```

**Describe alternatives you've considered**

Fixing all existing failures could help, but since the plugin doesn't always fail in CI, the list can grow again so it seems like a fruitless endeavor.

**Additional context**

Start by tracing how the plugin produces the advice list and how should-fail.txt determines whether the dependency-analysis check fails. Compare the current “Advice” output with the requested “Failure” distinction and define how individual failing advice entries should be identified. Done means CI users can tell which advice contributes to a failure without relying on the full list.

Written by the indexing model from the issue text.