Drop an unrelated file change from the branch

Reverting environment_variables.py in the previous commit checked it out from
origin/next rather than the merge base, which pulled AGENT_COMMIT_SHA from
another commit into this diff. This PR now touches only client.py and its test.

Author: chakrris

src/agentex/lib/environment_variables.py

@@ -25,7 +25,6 @@ class EnvVarKeys(str, Enum):
     AGENT_DESCRIPTION = "AGENT_DESCRIPTION"
     AGENT_ID = "AGENT_ID"
     AGENT_VERSION = "AGENT_VERSION"
-    AGENT_COMMIT_SHA = "AGENT_COMMIT_SHA"
     AGENT_API_KEY = "AGENT_API_KEY"
     # ACP Configuration
     ACP_URL = "ACP_URL"
@@ -68,12 +67,6 @@ class EnvironmentVariables(BaseModel):
     AGENT_ID: str | None = None
     # Build/version discriminator (image tag or git sha), set by the deployment
     AGENT_VERSION: str | None = None
-    # The agent's source commit, baked into the image or set by the deployment.
-    # Unlike AGENT_VERSION this is expected to be a git SHA and nothing else, and
-    # it is OPT-IN: nothing is stamped unless the agent calls
-    # `adk.code_revision.enable()`, which also refuses a value that is not a git
-    # object name. See agentex.lib.core.tracing.code_revision.
-    AGENT_COMMIT_SHA: str | None = None
     AGENT_API_KEY: str | None = None
     ACP_TYPE: str | None = "async"
     AGENT_INPUT_TYPE: str | None = None