feat: drop support for Python 3.9

[Copilot]

Overview

Drops Python 3.9 from all supported versions, bumping the minimum to Python 3.10. Also adds the missing Python 3.14 classifier to all packages. Aligns with ecosystem standards for EOL version removal.

Changes

• pyproject.toml (all 9 packages + validation): python = ">=3.9,<4.0" → python = ">=3.10,<4.0"; removed Programming Language :: Python :: 3.9 PyPI classifier; added missing Programming Language :: Python :: 3.14 PyPI classifier
• .github/workflows/build.yml: Removed "3.9" from both CI matrix definitions (build + validation jobs)
• CONTRIBUTING.md: Updated supported versions list
• .devcontainer/devcontainer.json: Removed Python 3.9 image option

Related Issue

Testing Instructions

• CI matrix no longer includes Python 3.9 — verify the build workflow runs cleanly against 3.10–3.14
• Confirm all packages install and pass tests on Python 3.10+: poetry install && poetry run pytest in each package directory
• Verify PyPI classifiers on all packages correctly list Python 3.10 through 3.14

[baywet]

@copilot python version 3.14 is missing from all the toml files. Let's take this opportunity to fix that. Use a fix: conventional commit for this one.

[Copilot]

@copilot python version 3.14 is missing from all the toml files. Let's take this opportunity to fix that. Use a fix: conventional commit for this one.

Fixed in 6c13439 — added "Programming Language :: Python :: 3.14" classifier to all 9 pyproject.toml files.

[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