fix(ci): resolve unit_tests and integration_tests CI failures

- Fix Rich Console line-wrapping breaking assertions in
  context_unit_tests_steps.py: collapse newlines before checking for
  filenames and overflow summaries (CI temp paths exceed 80 columns)
- Fix features.mocks import failure in database_integration.robot:
  replace hardcoded sys.path '/app' with portable ${CURDIR}/..
- Fix --load-context help text assertions in load_context_test.robot:
  merge stderr into stdout via stderr=STDOUT and remove duplicate test
- Add standalone dead_code nox session running vulture directly
- Rename security nox session to security_scan to match CI references
- Restore --exclude discovery to integration_tests nox session (lost
  during merge conflict resolution)

features/steps/context_unit_tests_steps.py

@@ -593,11 +593,13 @@ def step_check_already_tracked(context):
         f"Output: {context.result.output}"
     )
     clean_output = strip_ansi_codes(context.result.output)
+    # Collapse Rich line-wraps so long paths broken across lines are searchable
+    unwrapped_output = clean_output.replace("\n", "")
     assert "File(s) already in context" in clean_output, (
         f"Expected warning about already tracked files.\n"
         f"Output: {context.result.output}"
     )
-    assert "... and 2 more files" in clean_output, (
+    assert "... and 2 more files" in unwrapped_output, (
         f"Expected summary of remaining already tracked files.\n"
         f"Output: {context.result.output}"
     )
@@ -611,17 +613,19 @@ def step_check_already_tracked_without_summary(context):
         f"Output: {context.result.output}"
     )
     clean_output = strip_ansi_codes(context.result.output)
+    # Collapse Rich line-wraps so long paths broken across lines are searchable
+    unwrapped_output = clean_output.replace("\n", "")
     assert "File(s) already in context" in clean_output, (
         f"Expected warning about already tracked files.\n"
         f"Output: {context.result.output}"
     )
-    assert "... and" not in clean_output, (
+    assert "... and" not in unwrapped_output, (
         f"Did not expect overflow summary for fewer than 11 files.\n"
         f"Output: {context.result.output}"
     )
     if context.already_paths:
         expected_name = context.already_paths[0].name
-        assert expected_name in clean_output, (
+        assert expected_name in unwrapped_output, (
             f"Expected tracked file name '{expected_name}' in output.\n"
             f"Output: {context.result.output}"
         )