ci: avoid duplicate PR checks and run full CDA tests nightly

[krowvin]

Avoid duplicate tests on feature-branch pushes and move expensive CDA coverage to nightly/manual runs. Keep the existing standalone workflows, without a custom policy script, shared setup action, or aggregate merge gate.

• Unit tests and strict mypy run on Python 3.9 and latest stable (3.x) for all PRs and pushes to main. Formatting and CodeQL run on PRs/main; superseded PR runs are cancelled.
• The full 18-job CDA matrix runs nightly at 08:17 UTC and through manual dispatch. It no longer runs automatically on PRs or merges, and no longer repeats mypy in every matrix job. Cached environments still run dependency installation with binary-only dependencies.
• Keep exact-tag release testing and version validation before publishing, using latest stable Python. Preserve main's setup-python v7 upgrade.
• Document the simple trigger policy and manual integration command. Draft and documentation PRs receive the same lightweight checks as other PRs; there is no changed-file classification.

Validation: actionlint, configured YAML formatting, and whitespace checks pass. Parsed-workflow assertions verify standalone triggers, only Python 3.9/latest, and exactly 18 nightly CDA combinations. Python application code and dependencies are unchanged; the earlier local Python 3.9/3.14 mock tests and type checks passed. GitHub checks will validate the revised workflow head.

Tradeoff: CDA integration regressions may be found after merge. Maintainers can run gh workflow run CDA-testing.yml --ref <branch> before merging when needed. Repository admins should require the two unit-test checks, formatting, CodeQL, and existing external checks; nightly CDA jobs must not be required on PRs. This PR does not change repository rules or publish a package.

[krowvin]

Dialing this back a bit from the python scripts, they're a bit much and would be hard to maintain.

if for example someone wants to add a new doc extensions for doc deployment they might never think to go into a python script in the scripts directory to have this included.

[msweier]

Cool! Maybe add a note to CONTRIBUTING.MD about gh workflow run CDA-testing.yml --ref <branch> so we remember to run it before approving something? Or if we want to 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