fix(test): isolate parallel behave subprocesses with per-scenario temp databases

Each behave-parallel worker previously resolved to the same file-based
SQLite database (cleveragents.db or .cleveragents/db.sqlite) because
before_scenario removed the CLEVERAGENTS_DATABASE_URL env var and the
fallback paths are shared across processes.  Under parallel execution
this caused intermittent 'database is locked' and duplicate-project
errors—most visibly in the coverage_report nox session.

Replace the env-var removal in before_scenario with unique temp database
paths via tempfile.mktemp(), giving every scenario its own isolated
database file.  Temp files are cleaned up in after_scenario.

Also fix cli_streaming_steps.py where a Background + duplicate Given
sequence triggered a duplicate project name collision, and update
coverage_boost_steps.py so Settings-default assertions explicitly clear
the env vars before testing pydantic defaults.

features/environment.py

@@ -4,6 +4,7 @@ import contextlib
 import os
 import shutil
 import sys
+import tempfile
 from pathlib import Path
 
 LANGSMITH_ENV_VARS = [
@@ -32,10 +33,16 @@ def before_all(context):
     # Ensure tests never block on migration prompts or real providers
     os.environ.setdefault("CLEVERAGENTS_AUTO_APPLY_MIGRATIONS", "true")
     os.environ.setdefault("CLEVERAGENTS_TESTING_USE_MOCK_AI", "true")
-    os.environ.setdefault("CLEVERAGENTS_DATABASE_URL", "sqlite:///cleveragents.db")
-    os.environ.setdefault(
-        "CLEVERAGENTS_TEST_DATABASE_URL", "sqlite:///cleveragents_test.db"
-    )
+    # Use per-process unique database paths so parallel test subprocesses
+    # (behave-parallel) never contend on the same SQLite file.
+    if "CLEVERAGENTS_DATABASE_URL" not in os.environ:
+        os.environ["CLEVERAGENTS_DATABASE_URL"] = (
+            f"sqlite:///{tempfile.mktemp(suffix='.db', prefix='cleveragents_')}"
+        )
+    if "CLEVERAGENTS_TEST_DATABASE_URL" not in os.environ:
+        os.environ["CLEVERAGENTS_TEST_DATABASE_URL"] = (
+            f"sqlite:///{tempfile.mktemp(suffix='.db', prefix='cleveragents_test_')}"
+        )
     os.environ.setdefault("BEHAVE_TESTING", "true")
 
     # Set up mock AI provider for all tests
@@ -92,10 +99,17 @@ def before_scenario(context, scenario):
         if env_var in os.environ:
             del os.environ[env_var]
 
-    # Ensure each scenario starts with a fresh database URL so tests
-    # don't share persisted project state across runs
-    for env_var in ["CLEVERAGENTS_DATABASE_URL", "CLEVERAGENTS_TEST_DATABASE_URL"]:
-        os.environ.pop(env_var, None)
+    # Give each scenario a unique database file so scenarios cannot share
+    # persisted state AND parallel subprocesses never collide on the same
+    # SQLite file.  Store the paths for cleanup in after_scenario.
+    context._scenario_db_paths = []
+    for env_var, prefix in (
+        ("CLEVERAGENTS_DATABASE_URL", "cleveragents_"),
+        ("CLEVERAGENTS_TEST_DATABASE_URL", "cleveragents_test_"),
+    ):
+        db_path = tempfile.mktemp(suffix=".db", prefix=prefix)
+        os.environ[env_var] = f"sqlite:///{db_path}"
+        context._scenario_db_paths.append(db_path)
 
     # Re-apply mock AI provider after container reset
     try:
@@ -205,3 +219,10 @@ def after_scenario(context, scenario):
         MEMORY_ENGINES.clear()
     except ImportError:
         pass
+
+    # Remove per-scenario temp database files (and associated journal/WAL
+    # files) now that all engines have been disposed.
+    for db_path in getattr(context, "_scenario_db_paths", []):
+        for suffix in ("", "-journal", "-wal", "-shm"):
+            with contextlib.suppress(OSError):
+                os.unlink(db_path + suffix)

features/steps/cli_streaming_steps.py

@@ -31,6 +31,13 @@ def step_create_temp_dir(context):
     context.original_dir = os.getcwd()
     os.chdir(context.temp_dir)
 
+    # Give this invocation a unique database so repeated calls within the
+    # same scenario (e.g. Background + explicit Given) never collide.
+    db_path = tempfile.mktemp(suffix=".db", prefix="cleveragents_")
+    os.environ["CLEVERAGENTS_DATABASE_URL"] = f"sqlite:///{db_path}"
+    context._scenario_db_paths = getattr(context, "_scenario_db_paths", [])
+    context._scenario_db_paths.append(db_path)
+
     # Reset container for clean state
     from cleveragents.application.container import reset_container
 

features/steps/coverage_boost_steps.py

@@ -14,6 +14,10 @@ def step_create_settings(context):
     # Clear any existing singleton
     if hasattr(Settings, "_instance"):
         Settings._instance = None
+    # Remove database URL env vars so we test the actual pydantic defaults,
+    # not the per-scenario temp paths injected by environment.py.
+    for key in ("CLEVERAGENTS_DATABASE_URL", "CLEVERAGENTS_TEST_DATABASE_URL"):
+        os.environ.pop(key, None)
     context.settings = Settings()
 
 
@@ -44,6 +48,12 @@ def step_verify_production_status(context):
 @when("I get the database URL from Settings")
 def step_get_database_url(context):
     """Get database URL."""
+    # Clear singleton and database URL env vars so we test the actual
+    # pydantic defaults, not per-scenario temp paths from environment.py.
+    if hasattr(Settings, "_instance"):
+        Settings._instance = None
+    for key in ("CLEVERAGENTS_DATABASE_URL", "CLEVERAGENTS_TEST_DATABASE_URL"):
+        os.environ.pop(key, None)
     settings = Settings()
     context.db_url = settings.get_database_url()
     context.test_db_url = settings.get_database_url(test=True)