fix(cli): restore session list json contract

Ensure the session list helper only emits the documented fields so downstream consumers stay compliant, and tighten the Behave coverage to enforce the contract.\n\nISSUES CLOSED: #6436

features/session_cli.feature

@@ -39,10 +39,10 @@ Feature: Session CLI commands
     Then the session CLI output should be valid JSON
     And the session CLI JSON should contain "sessions"
 
-  Scenario: List sessions JSON includes token usage counts
+  Scenario: List sessions JSON matches the documented contract
     Given there are mocked existing sessions
     When I run session CLI list with --format json
-    Then the session CLI JSON list token usage should include counts
+    Then the session CLI JSON list entries should match the documented contract
 
   # Show command tests
   Scenario: Show session with valid ID

features/steps/session_cli_steps.py

@@ -525,18 +525,26 @@ def step_json_show_token_usage_counts(context: Context) -> None:
     _assert_token_usage_counts_are_ints(token_usage)
 
 
-@then("the session CLI JSON list token usage should include counts")
-def step_json_list_token_usage_counts(context: Context) -> None:
+@then("the session CLI JSON list entries should match the documented contract")
+def step_json_list_contract(context: Context) -> None:
     parsed = json.loads(context.result.output)
     data = _unwrap_envelope(parsed)
     sessions = data.get("sessions")
     assert isinstance(sessions, list), f"sessions missing or not a list: {sessions}"
     for index, session in enumerate(sessions):
-        token_usage = session.get("token_usage")
-        assert isinstance(token_usage, dict), (
-            f"token_usage missing for session {index}: {token_usage}"
+        assert isinstance(session, dict), (
+            f"session entry at index {index} is not an object: {session!r}"
+        )
+        expected_keys = {"id", "name", "actor", "messages", "updated"}
+        actual_keys = set(session.keys())
+        missing = expected_keys - actual_keys
+        extra = actual_keys - expected_keys
+        assert not missing, (
+            f"session entry {index} missing keys {sorted(missing)}: {session!r}"
+        )
+        assert not extra, (
+            f"session entry {index} has undocumented keys {sorted(extra)}: {session!r}"
         )
-        _assert_token_usage_counts_are_ints(token_usage)
 
 
 def _assert_token_usage_counts_are_ints(token_usage: dict[str, Any]) -> None:

src/cleveragents/cli/commands/session.py

@@ -133,11 +133,6 @@ def _session_list_dict(sessions: list[Session]) -> dict[str, Any]:
                 "actor": s.actor_name or "(none)",
                 "messages": s.message_count,
                 "updated": s.updated_at.isoformat(),
-                "token_usage": {
-                    "input_tokens": s.token_usage.input_tokens,
-                    "output_tokens": s.token_usage.output_tokens,
-                    "estimated_cost": f"${s.token_usage.estimated_cost:.4f}",
-                },
             }
         )