pip 26.1 adds lockfile support

pip 26.1 has ended support for Python 3.9. Since macOS's default python3 is still 3.9, I created a new virtual environment with Python 3.14 and confirmed 26.1 via pip install -U pip.

The core of the new features is twofold.

• pip lock datasette llm generates a 519-line pylock.toml lockfile containing Datasette and LLM along with all dependencies.
• --uploaded-prior-to P4D lets you install only packages that are at least 4 days old since upload. The format follows ISO 8601 duration, like P4D, but only day units are supported.

Using this option 3 days after LLM 0.31 was released resulted in LLM 0.30 being installed. This now enables an installation approach that doesn't immediately pick the newly uploaded version, but instead selects only versions that have passed a certain period.