feat(packaging): introduce slim agentex-sdk-client sibling package

Splits the published wheel into two namespace-sharing packages so REST-only
consumers (e.g. egp-api-backend, which currently hand-rolls clients to avoid
dep weight) can install just the Stainless surface without dragging in the
full ADK stack.

Existing consumers see no change: `pip install agentex-sdk` continues to
work; agentex-sdk now depends on agentex-sdk-client, so the bare REST client
deps install transitively. Both packages contribute disjoint files to the
agentex.* namespace.

New package layout:
- `agentex-sdk-client` (new, slim)
  - ships `agentex/{__init__.py, _*.py, _utils/, types/, resources/, py.typed}`
  - depends on httpx, pydantic, typing-extensions, anyio, distro, sniffio (6)
  - `pip install agentex-sdk-client` → 6 deps, `from agentex import Agentex` works

- `agentex-sdk` (existing, heavy)
  - ships only `agentex/lib/*` now
  - depends on `agentex-sdk-client` + the existing 31 ADK deps
  - `pip install agentex-sdk` → 6 + 31 = 37 deps, full surface

Verified locally with `python -m build --wheel` for both:
- Slim wheel: 154 files (all under agentex/{__init__.py, _*.py, _utils,
  types, resources, py.typed}), 6 Requires-Dist, no agentex/lib/* files
- Heavy wheel: only agentex/lib/* files, depends on agentex-sdk-client
- Dual install on Python 3.13: both work, no file conflicts, all imports
  resolve correctly

Follow-ups required before this can ship (see PR body):
- release-please-config.json: add the second package
- bin/publish-pypi: build + publish both wheels
- PyPI: claim the agentex-sdk-client package name (needs maintainer auth)
- Stainless dashboard: configure to emit / preserve client/pyproject.toml

Tracking: AGX1-292.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: max-parke-scale

client/README.md

@@ -0,0 +1,29 @@
+# agentex-sdk-client
+
+A lean REST client for the Agentex API. Provides the same `from agentex import Agentex, AsyncAgentex` entrypoints as `agentex-sdk` with only the dependencies the HTTP client actually needs (≈6 packages).
+
+## Installation
+
+```sh
+pip install agentex-sdk-client
+```
+
+## Usage
+
+```python
+from agentex import Agentex
+
+client = Agentex()
+# ... call methods on `client.<resource>.<method>(...)`
+```
+
+## When to use this vs `agentex-sdk`
+
+- **`agentex-sdk-client`** — you only need to call the Agentex REST API. No agent authoring, no Temporal workflows, no FastACP server, no provider integrations.
+- **`agentex-sdk`** — you're authoring agents. Pulls everything: ACP server, Temporal, MCP, LLM providers, observability, CLI.
+
+`agentex-sdk` depends on `agentex-sdk-client`, so if you install `agentex-sdk` you get the slim client transitively. The two packages contribute disjoint files to the `agentex.*` namespace — `agentex/lib/*` ships only from `agentex-sdk`.
+
+## Source
+
+This package is generated from the same Stainless project as `agentex-sdk`, at [scaleapi/scale-agentex-python](https://github.com/scaleapi/scale-agentex-python). The slim wheel includes only `agentex/{__init__.py, _*.py, _utils/, types/, resources/}` from the shared source tree.

client/pyproject.toml

@@ -0,0 +1,97 @@
+[project]
+name = "agentex-sdk-client"
+version = "0.0.1"
+description = "Lean REST client for the Agentex API. Provides `from agentex import Agentex, AsyncAgentex` and supporting types with the minimal dependency set."
+license = "Apache-2.0"
+authors = [
+  { name = "Agentex", email = "roxanne.farhad@scale.com" },
+]
+readme = "README.md"
+
+# Bare client surface only — the Stainless-generated REST client.
+# Everything ADK-related (agentex.lib.*) lives in the sibling agentex-sdk
+# package, which depends on this one.
+dependencies = [
+    "httpx>=0.28.1,<0.29",
+    "pydantic>=2.0.0, <3",
+    "typing-extensions>=4.14, <5",
+    "anyio>=3.5.0, <5",
+    "distro>=1.7.0, <2",
+    "sniffio",
+]
+
+requires-python = ">= 3.11,<4"
+classifiers = [
+  "Typing :: Typed",
+  "Intended Audience :: Developers",
+  "Programming Language :: Python :: 3.11",
+  "Programming Language :: Python :: 3.12",
+  "Programming Language :: Python :: 3.13",
+  "Programming Language :: Python :: 3.14",
+  "Operating System :: OS Independent",
+  "Topic :: Software Development :: Libraries :: Python Modules",
+  "License :: OSI Approved :: Apache Software License",
+]
+
+[project.urls]
+Homepage = "https://github.com/scaleapi/scale-agentex-python"
+Repository = "https://github.com/scaleapi/scale-agentex-python"
+
+[project.optional-dependencies]
+aiohttp = ["aiohttp>=3.10.10,<4", "httpx_aiohttp>=0.1.9"]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+# Map the Stainless-generated client surface (excluding agentex/lib/) from
+# the shared src tree into the slim wheel. agentex/lib/ ships from the
+# sibling agentex-sdk package; both contribute to the agentex.* namespace
+# via disjoint files.
+[tool.hatch.build.targets.wheel]
+bypass-selection = true
+
+[tool.hatch.build.targets.wheel.force-include]
+"../src/agentex/__init__.py" = "agentex/__init__.py"
+"../src/agentex/_base_client.py" = "agentex/_base_client.py"
+"../src/agentex/_client.py" = "agentex/_client.py"
+"../src/agentex/_compat.py" = "agentex/_compat.py"
+"../src/agentex/_constants.py" = "agentex/_constants.py"
+"../src/agentex/_exceptions.py" = "agentex/_exceptions.py"
+"../src/agentex/_files.py" = "agentex/_files.py"
+"../src/agentex/_models.py" = "agentex/_models.py"
+"../src/agentex/_qs.py" = "agentex/_qs.py"
+"../src/agentex/_resource.py" = "agentex/_resource.py"
+"../src/agentex/_response.py" = "agentex/_response.py"
+"../src/agentex/_streaming.py" = "agentex/_streaming.py"
+"../src/agentex/_types.py" = "agentex/_types.py"
+"../src/agentex/_version.py" = "agentex/_version.py"
+"../src/agentex/_utils" = "agentex/_utils"
+"../src/agentex/types" = "agentex/types"
+"../src/agentex/resources" = "agentex/resources"
+"../src/agentex/py.typed" = "agentex/py.typed"
+
+[tool.hatch.build.targets.sdist]
+bypass-selection = true
+
+[tool.hatch.build.targets.sdist.force-include]
+"../src/agentex/__init__.py" = "src/agentex/__init__.py"
+"../src/agentex/_base_client.py" = "src/agentex/_base_client.py"
+"../src/agentex/_client.py" = "src/agentex/_client.py"
+"../src/agentex/_compat.py" = "src/agentex/_compat.py"
+"../src/agentex/_constants.py" = "src/agentex/_constants.py"
+"../src/agentex/_exceptions.py" = "src/agentex/_exceptions.py"
+"../src/agentex/_files.py" = "src/agentex/_files.py"
+"../src/agentex/_models.py" = "src/agentex/_models.py"
+"../src/agentex/_qs.py" = "src/agentex/_qs.py"
+"../src/agentex/_resource.py" = "src/agentex/_resource.py"
+"../src/agentex/_response.py" = "src/agentex/_response.py"
+"../src/agentex/_streaming.py" = "src/agentex/_streaming.py"
+"../src/agentex/_types.py" = "src/agentex/_types.py"
+"../src/agentex/_version.py" = "src/agentex/_version.py"
+"../src/agentex/_utils" = "src/agentex/_utils"
+"../src/agentex/types" = "src/agentex/types"
+"../src/agentex/resources" = "src/agentex/resources"
+"../src/agentex/py.typed" = "src/agentex/py.typed"
+"README.md" = "README.md"
+"pyproject.toml" = "pyproject.toml"

pyproject.toml

@@ -8,13 +8,13 @@ authors = [
 { name = "Agentex", email = "roxanne.farhad@scale.com" },
 ]
 
+# `agentex-sdk` keeps shipping the full developer experience. The
+# Stainless-generated REST client (`from agentex import Agentex, AsyncAgentex`
+# and supporting `agentex/{_*.py,types,resources}`) now ships from the slim
+# sibling package `agentex-sdk-client`. Anyone who installs `agentex-sdk` gets
+# `agentex-sdk-client` transitively, so existing consumer code is unchanged.
 dependencies = [
-    "httpx>=0.28.1,<0.29",
-    "pydantic>=2.0.0, <3",
-    "typing-extensions>=4.14, <5",
-    "anyio>=3.5.0, <5",
-    "distro>=1.7.0, <2",
-    "sniffio",
+    "agentex-sdk-client",
     "typer>=0.16,<0.17",
     "questionary>=2.0.1,<3",
     "rich>=13.9.2,<14",
@@ -150,8 +150,12 @@ include = [
   "src/*"
 ]
 
+# This wheel ships only agentex/lib/* — the rest of the agentex.* namespace
+# (the Stainless-generated client) ships from the sibling agentex-sdk-client
+# package, which agentex-sdk pulls in as a runtime dep.
 [tool.hatch.build.targets.wheel]
-packages = ["src/agentex"]
+only-include = ["src/agentex/lib"]
+sources = ["src"]
 
 [tool.hatch.build.targets.sdist]
 # Basically everything except hidden files/directories (such as .github, .devcontainers, .python-version, etc)