Prepare release v319

[heroku-linguist]

Commits since the last release:

• Bump uv from 0.9.7 to 0.9.9 (Bump uv from 0.9.7 to 0.9.9 #1961)
• Always use local for vars inside functions (Always use local for vars inside functions #1960)
• Further improve .python-version and runtime.txt error handling (Further improve .python-version and runtime.txt error handling #1962)
• Improve the error message when the build data file has been deleted (Improve the error message when the build data file has been deleted #1963)
• Work around tmpfs default permissions regression in runc 1.3.3 (Work around tmpfs default permissions regression in runc 1.3.3 #1964)

For the full diff, see the compare view:
v318...main

[edmorley]

$ make publish
Checking environment...
Checking buildpack versions in sync...
Extracting changelog entry for this release...

- Updated uv from 0.9.7 to 0.9.9. ([#1961](https://github.com/heroku/heroku-buildpack-python/pull/1961))
- Improved the error message shown for `.python-version` files that contain unexpected ASCII control code characters. ([#1962](https://github.com/heroku/heroku-buildpack-python/pull/1962))
- Fixed Bash command substitution warnings from being shown if `runtime.txt` contains null byte characters. ([#1962](https://github.com/heroku/heroku-buildpack-python/pull/1962))
- Improved the error message shown if the buildpack's build data file is deleted by a pre/post-compile hook. ([#1963](https://github.com/heroku/heroku-buildpack-python/pull/1963))

Deploy as v319 [y/n]? y

Creating GitHub release...
https://github.com/heroku/heroku-buildpack-python/releases/tag/v319

Publishing to the Heroku Buildpack Registry...
Two-factor code: ********************************************
Publishing buildpack heroku/python... done
Publishing buildpack was successful

 Version Released At              Status    
 ─────── ──────────────────────── ───────── 
 319     2025-11-14T20:43:37.181Z published