feat(packaging)!: introduce slim agentex-sdk-client + heavy agentex-sdk split

[max-parke-scale]

Stacked on #371. Do not merge until #371 lands.

Summary

Publishes the existing agentex-sdk wheel as two namespace-sharing packages so REST-only consumers can install just the Stainless REST surface without dragging in the full ADK runtime.

Install command	Deps	Ships
pip install agentex-sdk-client	6	agentex/{__init__.py, _*.py, _utils/, types/, resources/, protocol/, py.typed}
pip install agentex-sdk	6 (transitive) + 31 ADK	only agentex/lib/*; depends on agentex-sdk-client

The two packages contribute disjoint files to the agentex.* namespace. Existing pip install agentex-sdk consumers see no change: heavy depends on slim, so the slim deps install transitively.

Motivating consumer: packages/egp-api-backend hand-rolls a ~600-line JSON-RPC gateway today because it can't import the typed wire shapes without pulling in temporalio, fastapi, claude-agent-sdk, and 28 other deps. With this split + #371 (which moves protocol types to agentex.protocol.*), that gateway can pin agentex-sdk-client and use from agentex.protocol.acp import RPCMethod, CreateTaskParams, ....

Tracking: AGX1-292.

Note on the PR stack

This change was originally drafted as a single large PR (history visible in the force-push). On review it was clearly two distinct concerns, so it's been split:

• refactor(types): promote protocol types to agentex.protocol.* #371 — refactor only: move protocol types from agentex.lib.types.* to agentex.protocol.* with back-compat shims. Zero install-time impact.
• This PR (feat(packaging)!: introduce slim agentex-sdk-client + heavy agentex-sdk split #370) — packaging: introduce the second wheel and the release plumbing.

Reviewing them separately should be much more tractable.

Repo layout after merge

scale-agentex-python/
├── pyproject.toml                # Stainless-managed: agentex-sdk-client
│                                 # 6 deps, requires-python >= 3.11
│                                 # wheel `exclude` keeps lib/ out of the slim wheel
├── src/agentex/                  # shared source tree
│   ├── __init__.py, _*.py, _utils/, types/, resources/   # Stainless-generated
│   ├── protocol/                                          # (from #371)
│   └── lib/                                               # hand-authored ADK overlay
└── adk/                          # hand-authored — preserved via keep_files
    ├── pyproject.toml            # agentex-sdk
    │                             # depends on agentex-sdk-client>=0.11.4,<0.12
    │                             #          + 31 ADK deps
    │                             # requires-python >= 3.12
    │                             # wheel: force-include ../src/agentex/lib → agentex/lib
    └── README.md

src/agentex/lib/ stays where it is — Stainless already preserves it per CONTRIBUTING.md. The slim wheel's [tool.hatch.build.targets.wheel].exclude keeps lib/ out of the slim. The heavy wheel uses hatchling force-include "../src/agentex/lib" = "agentex/lib" to pull lib/ into the heavy. Same source file, two disjoint wheels.

Python-version pins

• agentex-sdk-client: requires-python = ">= 3.11,<4". Zero 3.12-only imports in the Stainless surface.
• agentex-sdk: requires-python = ">= 3.12,<4". agentex/lib/* uses from typing import override (3.12+ stdlib) in 19 files. The combined package's prior >= 3.11 pin was de-facto broken on 3.11; this PR aligns the pin with what actually works.

Release / publish wiring

• bin/publish-pypi: publishes slim before heavy. Heavy depends on slim, so flipping the order means a slim-side failure (token, transient PyPI 5xx, name collision) aborts before we ship a heavy that pins an unreleased slim.
• bin/check-release-environment: validates both AGENTEX_SDK_CLIENT_PYPI_TOKEN and AGENTEX_PYPI_TOKEN, with legacy PYPI_TOKEN as fallback.
• .github/workflows/publish-pypi.yml: passes both token secrets to the script.
• release-please-config.json: two-package mode (. and adk/) with include-component-in-tag = true. Tag scheme changes from v0.11.4 → agentex-sdk-client-v0.11.4 / agentex-sdk-v0.11.4 — flagged with ! in the title and commit. Any downstream tooling filtering by raw v* tags will need updating.
• .release-please-manifest.json: seeds adk/ at 0.11.4 so the first release produces matched versions.
• CI build job: builds both wheels via rye build --wheel (the --wheel flag is important — sdist-then-wheel-from-sdist can't resolve adk's cross-directory force-include from inside an unpacked sdist tarball).

Required maintainer follow-ups before this can ship

• Stainless dashboard:
  • Add adk/** to keep_files so the ADK overlay persists across codegen.
  • Reduce the dashboard's emitted dep list for root pyproject.toml to the 6 slim-base deps. (See "Risks" below — if this isn't done, every Stainless regen will silently re-add the 31 ADK deps to slim's dependencies = [...].)
• PyPI: claim the agentex-sdk-client package name; add AGENTEX_SDK_CLIENT_PYPI_TOKEN to repo secrets. agentex-sdk publishing continues using AGENTEX_PYPI_TOKEN from adk/.
• Verify: after Stainless dashboard config, trigger a Stainless regen and confirm adk/ survives and root pyproject's slim shape isn't clobbered.

Planned follow-up PRs

• D (in this repo): post-codegen CI guardrail asserting root pyproject.toml's dependencies = [...] is exactly the 6-dep slim set. Catches dashboard drift if Stainless re-adds ADK deps.
• E (in scaleapi/scaleapi): migrate packages/egp-api-backend from hand-rolled JSON-RPC to typed agentex.protocol.acp shapes; pin agentex-sdk-client. ~600 lines of dict-literal construction become typed model usage.
• Lockfile regeneration: requirements.lock / requirements-dev.lock need refresh after rye sync against the workspace; not yet committed because the local env doesn't have rye installed. Easy to fix in this PR if reviewers want, or as a fast-follow.
• README split: the root README.md describes capabilities the slim doesn't ship; deferring to its own PR so this one stays focused on packaging.
• agentex.__version__ policy: release-please-config.json's extra-files updates only root _version.py, so the runtime __version__ reflects the slim only. Either lockstep-version both (recommended, since they're co-released) or add a separate agentex.lib.__version__.

Verification (local)

# Slim wheel
python -m build --wheel
unzip -p dist/agentex_sdk_client-*.whl '*.dist-info/METADATA' | grep ^Name
# Name: agentex-sdk-client
unzip -p dist/agentex_sdk_client-*.whl '*.dist-info/METADATA' | grep -cE "^Requires-Dist:" | grep -v "extra =="
# 6
unzip -l dist/agentex_sdk_client-*.whl | grep -c "agentex/lib"
# 0  (lib excluded)
unzip -l dist/agentex_sdk_client-*.whl | grep -c "agentex/protocol"
# 3  (from #371)

# Heavy wheel
(cd adk && python -m build --wheel)
unzip -p adk/dist/agentex_sdk-*.whl '*.dist-info/METADATA' | grep "agentex-sdk-client"
# Requires-Dist: agentex-sdk-client<0.12,>=0.11.4
unzip -l adk/dist/agentex_sdk-*.whl | awk '{print $4}' | grep "^agentex/" | grep -v "^agentex/lib"
# (empty — only lib/* in heavy)

# Dual install on Python 3.13
python3.13 -m venv /tmp/c && /tmp/c/bin/pip install \
  dist/agentex_sdk_client-*.whl adk/dist/agentex_sdk-*.whl
/tmp/c/bin/python -c "
from agentex import Agentex                                          # slim
from agentex.protocol.acp import RPCMethod, CreateTaskParams         # slim (from #371)
from agentex.lib.utils.logging import make_logger                    # heavy
from agentex.lib.types.acp import RPCMethod as RM2                   # heavy (shim from #371)
assert RPCMethod is RM2  # shim re-exports canonical
print('OK')
"
# OK

Risks

• Stainless dashboard dep-list is more load-bearing than the wheel exclude. The slim's [tool.hatch.build.targets.wheel].exclude = ["src/agentex/lib/**"] is a hand-edit to Stainless's emitted file. Manual edits to dependencies = [...] survive Stainless 3-way merge historically (~7 confirmed examples from git log). We're betting the wheel-target exclude survives the same way. If it gets clobbered, the slim wheel would start re-including lib/ and conflict with the heavy on install. Detection: PR D's guardrail check catches it. Mitigation if it happens: re-add manually or move the exclude to the Stainless dashboard if configurable.
• Tag scheme change. Downstream tooling filtering by v* tags needs to update — flagged with ! in title/commit per Conventional Commits.
• adk/ sdist support deferred. Wheels publish fine; sdist for adk/ doesn't because rye build's default sdist-then-wheel-from-sdist flow can't resolve the cross-directory force-include. PyPI tolerates wheel-only releases; if reviewers want sdist support, options are (a) configure hatchling to copy ../src/agentex/lib into the sdist, or (b) explicitly disable sdist for adk/.
• agentex-sdk-client version pin in adk/pyproject.toml is >=0.11.4,<0.12. Release-please doesn't automatically bump this when slim moves; bumping the range is a manual step each minor/major. Comment in the file flags it. A release-please plugin or a small CI substitution rule could automate this in a follow-up.