[carloshvp]

Python 3.9 compatibility jobs fail in actions/setup-python when ubuntu-latest selects Ubuntu 26.04. The official Python toolchain manifest publishes 3.9.25 for Ubuntu 22.04 and 24.04, so these jobs stop before running tests. See the failed Copilot job.

Select ubuntu-24.04 for the Python 3.9 entries in the capture-core, Codex, Copilot, Cursor, Gemini CLI, and Windsurf matrices. Newer Python entries continue using ubuntu-latest, and all declared compatibility versions remain covered.

Validation:

• Repository-pinned actionlint 1.7.12 passes across all workflows; local external ShellCheck and pyflakes integrations were disabled because those tools are unavailable.
• Verified that the entire patch consists of the six runner expressions, with git diff --check passing.
• Confirmed the current official toolchain manifest contains an x64 Ubuntu 24.04 build for Python 3.9.25 and none for Ubuntu 26.04.
• All six hosted Python 3.9 jobs pass on ubuntu-24.04, including their test steps. Hosted actionlint passes; 60 checks are successful on this head.

Remaining CI: the weight-custody-manifest job fails with ModuleNotFoundError: OpenSSL, matching the unmodified main failure. Existing #362 supplies that separate dependency repair.

Refs #370.