feat: ship a useful default Python init template

[grouville]

Why

Today, dagger module init python hello creates a valid module whose object only contains pass. It works, but it does not show a new user how to turn their workspace into something useful.

For the 1.0 experience tracked in dagger/dagger#13626, the default should be a small working example. This follows the direction established by dagger/typescript-sdk#10.

What changes

The new default stores a filtered view of the caller's workspace and exposes a container function with that source mounted at /src. It uses Alpine 3.24 by default, while keeping the image configurable.

The template stays deliberately generic: it does not assume the workspace is a Python project, uses uv, or has a particular build command. uv is only used to package the generated Dagger module.

The previous blank template is now available as --template empty. legacy is unchanged, and an explicitly empty template value continues to select the default for compatibility.

The generated project files also move to Python 3.14 and accept uv_build releases below 0.12. The lower bound remains compatible with the uv version already bundled in the engine.

Why create instead of __init__

The template uses the Python SDK's supported alternate create constructor. It receives the caller's workspace and converts it into the fields Dagger stores between function calls. This keeps the user-facing workspace input separate from the state Dagger needs to restore later.

Try it

From an empty Git repository:

dagger sdk install github.com/grouville/python-sdk@feat/default-template --name python -y
dagger module init python hello -y
dagger api functions hello
dagger api call hello container \
  with-exec --args sh --args -c --args 'test -f /src/dagger.toml && pwd' \
  stdout

dagger api functions hello should list container, and the final command should print /src.

To check the blank template:

dagger module init python blank --template empty -y
sed -n '1,20p' .dagger/modules/blank/src/blank/__init__.py

The generated Blank class should contain only pass.

Verification

dagger check e-2-e:template-check
dagger check

All 12 checks pass against v1.0.0-beta.7 and the locally rebuilt engine from dagger/dagger@7a6730c178228b4a3a8273664d319578892b7fe1. A fresh generated module also returned Alpine 3.24.1 when invoked with the beta.7 CLI.