fix(tests): align BDD scenarios with rollback-removal behaviour (PR #8179)

Three CI gates were failing on this PR; this commit addresses the root
causes for each:

* lint (ruff format): drop the blank line between the docstring close
  and first statement in step_pr_create_with_error, and add the missing
  second blank line between step_pr_check_remove_link_persisted and the
  "Data integrity BDD step extensions" section comment block.

* unit_tests: two scenarios were inverted by `@tdd_expected_fail` on
  post-fix assertions, masking unrelated test-logic problems.
  - Remove `@tdd_expected_fail` from both `@tdd_issue_8179` scenarios in
    project_repository.feature - they describe post-fix behaviour and
    must report PASS as PASS, not as inverted-FAIL.
  - Drop the "Given project exists" precondition from the Update-non-
    existent scenario; the Background already initialises the in-memory
    DB and creating the same project being "updated as non-existent" is
    self-contradictory (caused the prior scenario to silently report
    inverted-PASS while actually never raising).
  - Update the OperationalError scenario in database_repository_coverage
    to assert the post-fix invariant: the repository no longer calls
    session.rollback() itself; that responsibility is delegated to the
    outer UnitOfWork.  Step text + assertion both flipped.

ISSUES CLOSED: #8179

features/database_repository_coverage.feature

@@ -42,7 +42,7 @@ Feature: Database Repository Error Handling Coverage
     Given I have a project repository with a session that fails on create
     When I attempt to create a project named "failing-project" with that failing session
     Then a database error should be raised when creating the project
-    And the session rollback should be triggered for the project create failure
+    And the session rollback should not be triggered for the project create failure
 
   @phase1
   Scenario: ProjectRepository get_by_id wraps OperationalError in DatabaseError

features/project_repository.feature

@@ -149,14 +149,13 @@ Feature: Namespaced project repository operations
 
   # ---------- Data integrity: rollback removal verification ----------
 
-  @tdd_issue @tdd_issue_8179 @tdd_expected_fail
+  @tdd_issue @tdd_issue_8179
   Scenario: IntegrityError raises DatabaseError through repository create method (no explicit rollback)
     Given a namespaced project "local/integrity-verify" exists in the repository
     When I create a namespaced project "local/integrity-verify" via the repository expecting an error
     Then the repository error should be "DatabaseError"
 
-  @tdd_issue @tdd_issue_8179 @tdd_expected_fail
+  @tdd_issue @tdd_issue_8179
   Scenario: Update non-existent project raises ProjectNotFoundError without leaving transaction dirty
-    Given a namespaced project "local/missing-update-check" exists in the repository
     When I update a non-existent project "local/missing-update-check" expecting an error
     Then the repository error should be "ProjectNotFoundError"

features/steps/container_and_repository_coverage_steps.py

@@ -378,10 +378,14 @@ def step_verify_create_database_error(context):
     assert isinstance(context.create_error, DatabaseError)
 
 
-@then("the session rollback should be triggered for the project create failure")
+@then("the session rollback should not be triggered for the project create failure")
 def step_verify_create_rollback(context):
-    """Verify session rollback executed on create failure."""
-    assert context.session_mock.rollback.call_count >= 1
+    """Verify session rollback NOT executed by the repository on create failure.
+
+    Per PR #8179, ``ProjectRepository.create()`` no longer calls
+    ``session.rollback()`` itself — the outer UnitOfWork owns rollback.
+    """
+    assert context.session_mock.rollback.call_count == 0
 
 
 @given("I have a project repository with a session that fails on query")

features/steps/project_repository_steps.py

@@ -566,6 +566,7 @@ def step_pr_removed_link_absent_new_session(context: Any) -> None:
     finally:
         new_session.close()
 
+
 # ---------------------------------------------------------------------------
 # Data integrity BDD step extensions (PR #8179)
 # ---------------------------------------------------------------------------
@@ -584,7 +585,6 @@ def step_pr_create_with_error(context: Any, ns_name: str) -> None:
     redundant ``session.rollback()`` was removed from exception handlers —
     ``session.rollback()`` now fires in the ``finally`` block instead.
     """
-
     project = _make_project(ns_name)
     try:
         context.pr_project = context.pr_project_repo.create(project)