Split the worker into a distribution of its own

A cluster or GPU host installs `pip install fluksio-worker` and gets the
agent and the runner, not psycopg, numpy and the MCP SDK. The engine
depends on it as a workspace member, so the file it launches node code
with is the same file a remote worker runs — which is what keeps a node
unable to tell the difference. Copying the two files by hand still works.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

backend/pyproject.toml

@@ -28,8 +28,12 @@ dependencies = [
     "influxdb-client[async]>=1.40.0",
     "croniter>=1.3.0",
     "mcp>=1.29,<2",
+    "fluksio-worker>=0.1,<0.2",
 ]
 
+[tool.uv.sources]
+fluksio-worker = { workspace = true }
+
 [dependency-groups]
 dev = [
     "pytest<8.0.0,>=7.4.3",
@@ -42,6 +46,11 @@ dev = [
 [tool.hatch.build.targets.wheel]
 packages = ["fluksio"]
 
+# Named rather than excluded: this directory also holds a working tree's
+# runtime data — `flow-data/` with the user venv in it — which is not source.
+[tool.hatch.build.targets.sdist]
+include = ["fluksio", "tests", "scripts", "alembic.ini", "pyproject.toml", "README.md"]
+
 [build-system]
 requires = ["hatchling"]
 build-backend = "hatchling.build"
@@ -92,12 +101,6 @@ ignore = [
 # Printing is what this one is about: node code is user code, and `print` is
 # how it says things.
 "tests/flow/test_logs.py" = ["ARG001", "T201"]
-# This one takes its own directory off sys.path before the rest of its imports
-# run, which is the whole point of doing it there.
-"fluksio/flow/worker_main.py" = ["E402"]
-# A standalone script copied onto another machine: it has no logger configured
-# before it tells you the one dependency it is missing.
-"fluksio/worker/fluksio_worker.py" = ["T201"]
 
 [tool.ruff.lint.pyupgrade]
 # Preserve types, even if a file imports `from __future__ import annotations`.