Discover sample packages instead of listing them

[brianstrauch]

Problem

The wheel target listed every sample directory by hand, and hatchling's packages setting takes literal paths — it does not accept patterns — so the list had to be maintained manually. It drifted, silently: an entry naming a directory that does not exist is ignored without a warning.

• nexus was added in Nexus samples #174, where the directory was actually hello_nexus, so it has never matched anything.
• 14 sample directories added since the uv migration (Migrate to uv #170) were never shipped, including google_adk_agents and openai_agents.
• The sdist shipped no samples at all — 6 entries total.

#170 called this out when it introduced the list: "contributors will have to explicitly add samples to this list... I haven't yet found a way to automatically add top-level directories matching a pattern as packages." Poetry's previous config globbed ({include = "**/*.py", from = "."}); the hatchling translation could not.

Change

Switch the build backend to setuptools and let packages.find discover the samples, so adding a sample needs no build config change:

[tool.setuptools.packages.find]
exclude = ["lambda_worker*"]

[build-system]
requires = ["setuptools>=77"]
build-backend = "setuptools.build_meta"

Net -51 lines: the 33-entry list, both hatch build targets, the sources mapping, and [tool.hatch.metadata] all go away. setuptools>=77 is the floor for PEP 639 (license = "MIT" as a string), verified by building under that constraint.

Namespace discovery (the default) is required: openai_agents/* and message_passing/update_with_start/lazy_initialization have subdirectories without an __init__.py, and namespaces = false drops 122 files.

Verification

• Wheel and sdist each contain exactly the 652 tracked sample .py files — a set match against git ls-files — with no venv, cache, lambda_worker, or .github content. The wheel previously had 405; the sdist had none.
• A wheel install and an editable install both import samples the old list omitted (google_adk_agents, openai_agents); running a sample script by path still resolves its absolute imports.
• pytest tests/strands_plugin tests/langgraph_plugin tests/google_adk_agents — 27 passed against the reinstalled editable project.

Notes

• setuptools writes temporalio_samples.egg-info/ into the working tree, hence the .gitignore addition.
• Editable installs now use setuptools' package-map finder rather than a root .pth, so a brand-new sample directory is not importable by path until uv sync re-runs. CI is unaffected (it syncs after checkout), and pytest is unaffected (rootdir goes on sys.path).
• Alternatives considered: uv_build documents no support for multiple top-level modules (its module-name list form is discouraged, and would be the same 47-entry enumeration); uv's recommended workspace layout would need 47 member manifests plus nesting every sample a level deeper, which changes 237 documented uv run <path> commands and every deep link.

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