fix(cli): update test assertions for new session create JSON structure

Update feature file assertions to match the new nested JSON structure
for session create output. Changed assertions from 'session_id:' to 'id:'
to reflect the new data.session.id structure per spec #6441.

features/security_template_coverage_boost.feature

@@ -139,7 +139,7 @@ Feature: Coverage boost for security template branch
     Given a session CLI test environment
     And a mock session service that returns a created session
     When I invoke session create with format "json"
-    Then the covboost session output should contain "session_id"
+    Then the covboost session output should contain "data"
 
   Scenario: Session create error shows session not found message
     Given a session CLI test environment
@@ -169,7 +169,7 @@ Feature: Coverage boost for security template branch
     Given a session CLI test environment
     And a mock session service that can export
     When I invoke session export to stdout
-    Then the covboost session output should contain "session_id"
+    Then the covboost session output should contain "data"
 
   Scenario: Session export to file that exists without force fails
     Given a session CLI test environment

features/session_create_error.feature

@@ -14,7 +14,7 @@ Feature: Session create command resolves DI container wiring
   Scenario: Session create produces a new session
     When I invoke session-create-error create with no arguments
     Then the session-create-error command should exit successfully
-    And the session-create-error output should contain "session_id:"
+    And the session-create-error output should contain "id:"
 
   @tdd_issue @tdd_issue_570
 
@@ -30,7 +30,7 @@ Feature: Session create command resolves DI container wiring
     When I invoke session-create-error create with actor "openai/gpt-4"
     Then the session-create-error command should exit successfully
     And the session-create-error output should contain "openai/gpt-4"
-    And the session-create-error output should contain "session_id:"
+    And the session-create-error output should contain "id:"
 
   @tdd_issue @tdd_issue_570