Don't split on pragma markers

[zsol]

Description

Pragma comments have similar semantics as # type: ignore, so they should be treated similarly: lines marked with them are fine to merge (this generally extends the scope of the suppression/pragma) but not OK to split.

Note: this changes the stable style; I'm not sure if that's OK in this case or not, but happy to rework this under a preview style flag if that's the only concern.

Checklist - did you ...

• Add an entry in CHANGES.md if necessary?
• Add / update tests if necessary?
• Add new / update outdated documentation?

[github-actions]

diff-shades results comparing this PR (5456363) to main (58f31a7). The full diff is available in the logs under the "Generate HTML diff report" step.

╭──────────────────────── Summary ────────────────────────╮
│ 5 projects & 50 files changed / 471 changes [+116/-355] │
│                                                         │
│ ... out of 2 514 425 lines, 11 770 files & 23 projects  │
╰─────────────────────────────────────────────────────────╯

Differences found.

What is this? | Workflow run | diff-shades documentation

[amyreese]

I would also like to see this with a configurable set of additional "pragma" comments. Eg, Fixit uses # lint-ignore: CODE and # lint-fixme: CODE that would be nice to be included in this feature, while # usort: skip or # isort: skip might also be useful.