Constrain PyPI development publishing

[josephbirkner]

Summary

The post-merge main deployment reached PyPI's 10 GB per-project quota while uploading 2026.3.6.dev6. Public package metadata currently accounts for about 9.92 GiB: approximately 7.30 GiB is development previews and 2.54 GiB is final releases.

This stops unbounded duplicate publication while preserving the preview path requested for releases:

• publish development wheels only for release/X.Y.Z pull requests targeting main
• continue running the complete wheel matrix on ordinary main pushes, but skip PyPI upload
• continue publishing final vX.Y.Z tag builds
• document deletion of superseded previews as part of release retention

Old previews still need a one-time manual purge through PyPI's project management UI because PyPI does not expose release deletion through its package API.

Validation

• YAML parsing with PyYAML
• actionlint v1.7.12
• git diff --check

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

Package	Line Rate	Branch Rate	Health
libs.geojsonsource.include.geojsonsource	100%	50%	✔
libs.geojsonsource.src	66%	38%	➖
libs.gridsource.include.gridsource	0%	0%	❌
libs.gridsource.src	0%	0%	❌
libs.http-datasource.src	48%	26%	❌
libs.http-service.src	58%	24%	➖
libs.location.include.mapget.location	100%	100%	✔
libs.location.src	83%	40%	✔
libs.logging.include.mapget	5%	2%	❌
libs.model.include.mapget.model	51%	30%	➖
libs.model.src	73%	42%	➖
libs.service.include.mapget.service	56%	50%	➖
libs.service.src	74%	38%	➖
Summary	65% (12147 / 18562)	35% (12929 / 37286)	➖

Minimum allowed line rate is 50%