fix(publish): make publish-pypi idempotent across two-tag release cycles

release-please-config.json uses include-component-in-tag = true, so each
release cycle emits two GitHub release events (agentex-sdk-client-vX.Y.Z
and agentex-sdk-vX.Y.Z). Both events fire publish-pypi.yml, which calls
this script — the script unconditionally publishes both wheels per run,
so the second event's run tries to re-upload artifacts already on PyPI.

Under `set -eux`, twine's non-zero exit on a duplicate upload aborts the
script and turns the GitHub Action red on every other release cycle.

Add --skip-existing to both rye publish invocations. rye 0.44.0 forwards
this flag to `python -mtwine upload --skip-existing`; twine then treats
already-present files as exit 0 with a WARNING in place of HTTPError.

Verified locally against pypiserver: without the flag the second publish
exits non-zero, with the flag it logs `WARNING Skipping ... appears to
already exist` and exits 0.

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

Author: max-parke-scale

bin/publish-pypi

@@ -22,7 +22,7 @@ set -eux
 # Slim Stainless-managed client (root) — `agentex-sdk-client` on PyPI.
 mkdir -p dist
 rye build --clean --wheel  # --wheel: sdist deferred (see adk/pyproject.toml).
-rye publish --yes --token="${AGENTEX_SDK_CLIENT_PYPI_TOKEN:-$PYPI_TOKEN}"
+rye publish --yes --skip-existing --token="${AGENTEX_SDK_CLIENT_PYPI_TOKEN:-$PYPI_TOKEN}"
 
 # Heavy ADK overlay (adk/) — `agentex-sdk` on PyPI; pins the slim above.
 (
@@ -31,5 +31,5 @@ rye publish --yes --token="${AGENTEX_SDK_CLIENT_PYPI_TOKEN:-$PYPI_TOKEN}"
   # --wheel load-bearing: rye's sdist-then-wheel default can't resolve
   # the force-include of ../src/agentex/lib → silent empty wheel.
   rye build --clean --wheel
-  rye publish --yes --token="${AGENTEX_PYPI_TOKEN:-$PYPI_TOKEN}"
+  rye publish --yes --skip-existing --token="${AGENTEX_PYPI_TOKEN:-$PYPI_TOKEN}"
 )