Check that intended python version is being used

Don't use setup-python action

Deliberate error

Install python on $PATH in addition to in virtualenv

Revert "Don't use setup-python action"

This reverts commit 47b28be.

Don't use uv --preview to install

Revert "Deliberate error"

This reverts commit 0778ee8.

Specify python version with `uv sync`

partial revert

Author: dandavison

README.md

@@ -1849,7 +1849,7 @@ poe test -s --log-cli-level=DEBUG -k test_sync_activity_thread_cancel_caught
 #### Proto Generation and Testing
 
 To allow for backwards compatibility, protobuf code is generated on the 3.x series of the protobuf library. To generate
-protobuf code, you must be on Python <= 3.10, and then run `uv add "protobuf<4"` + `uv sync --all-extras`. Then the
+protobuf code, run `uv add "protobuf<4" --python 3.10` + `uv sync --all-extras --python 3.10`. Then the
 protobuf files can be generated via `poe gen-protos`. Tests can be run for protobuf version 3 by setting the
 `TEMPORAL_TEST_PROTO3` env var to `1` prior to running tests.