consider convention principle for `disableAllWarnings=true`

Considering:
- https://github.com/diffplug/spotless/pull/2766
- https://github.com/diffplug/spotless/issues/2745
- https://github.com/diffplug/spotless/issues/2745#issuecomment-3566971268

it feels overwhelming and impractical to require explicitly setting `disableAllWarnings=true`.
This should actually be part of a *convention-based default* to avoid unpleasant situations like the one recently discovered in Spotless.

In fact, this *should* be the default, because:

- Having thousands of warnings simply does not scale on a human level.
- It is unrealistic to expect developers to spend time dealing with such a volume of noise.
Most won’t have the time—or the motivation—to address it. Instead, the logs get flooded, attention gets diluted, and the natural reaction is to ignore the warnings entirely.
- Endless, repeating warnings create alert fatigue. The more noise a tool produces, the less likely real issues will ever be noticed.
- Warnings should be actionable by default.
If they aren’t, developers shouldn’t have to manually opt out. Tools should provide clean, helpful feedback out of the box.
- A tool that produces more noise than value becomes counterproductive.
Reducing irrelevant output is essential to maintaining a healthy signal-to-noise ratio.

From this perspective, having `disableAllWarnings=true` as the default would **establish a more sensible, error-focused baseline**.
Developers could then intentionally opt in to warnings when they want to focus on quality checks or refactoring, instead of being overwhelmed by default.