fix: Prevent 'main' project from being recreated after removal (#397)

Fixed the bug where removing a project (especially 'main') would cause
it to reappear in the project list on the next command execution.

Root cause: model_post_init() was forcing 'main' to exist on every
config load, even after explicit removal.

Changes:
- Updated model_post_init() to only create 'main' if no projects exist
- Fixed default_project handling to use first available project instead
  of always defaulting to 'main'
- Added integration test test_remove_default_project_issue_397() to
  verify the fix and prevent regression

The fix ensures users can remove any project (including 'main') as long
as they have at least one other project configured.

Co-authored-by: Paul Hernandez <phernandez@users.noreply.github.com>

src/basic_memory/config.py

@@ -192,15 +192,16 @@ class BasicMemoryConfig(BaseSettings):
 
     def model_post_init(self, __context: Any) -> None:
         """Ensure configuration is valid after initialization."""
-        # Ensure main project exists
-        if "main" not in self.projects:  # pragma: no cover
+        # Ensure at least one project exists
+        if not self.projects:  # pragma: no cover
             self.projects["main"] = (
                 Path(os.getenv("BASIC_MEMORY_HOME", Path.home() / "basic-memory"))
             ).as_posix()
 
-        # Ensure default project is valid
+        # Ensure default project is valid (points to an existing project)
         if self.default_project not in self.projects:  # pragma: no cover
-            self.default_project = "main"
+            # Set default to first available project
+            self.default_project = next(iter(self.projects.keys()))
 
     @property
     def app_database_path(self) -> Path:

test-int/cli/test_project_commands_integration.py

@@ -119,3 +119,50 @@ def test_project_set_default(app_config, config_manager):
         for line in lines:
             if "another-project" in line:
                 assert "[X]" in line
+
+
+def test_remove_default_project_issue_397(app_config, test_project, config_manager):
+    """Test that a removed project does not reappear in project list (issue #397).
+
+    Reproduces the bug where removing a project would cause it to be
+    recreated on the next config load.
+    """
+    runner = CliRunner()
+
+    # Use a separate temporary directory to avoid nested path conflicts
+    with tempfile.TemporaryDirectory() as temp_dir:
+        new_project_path = Path(temp_dir) / "newmain"
+        new_project_path.mkdir()
+
+        # Step 1: Add a new project
+        result = runner.invoke(app, ["project", "add", "newmain", str(new_project_path)])
+        if result.exit_code != 0:
+            print(f"STDOUT: {result.stdout}")
+            print(f"STDERR: {result.stderr}")
+        assert result.exit_code == 0
+
+        # Step 2: Set the new project as default
+        result = runner.invoke(app, ["project", "default", "newmain"])
+        if result.exit_code != 0:
+            print(f"STDOUT: {result.stdout}")
+            print(f"STDERR: {result.stderr}")
+        assert result.exit_code == 0
+
+        # Step 3: Remove the original default project
+        result = runner.invoke(app, ["project", "remove", "test-project"])
+        if result.exit_code != 0:
+            print(f"STDOUT: {result.stdout}")
+            print(f"STDERR: {result.stderr}")
+        assert result.exit_code == 0
+
+        # Step 4: Verify removed project does NOT appear in list
+        result = runner.invoke(app, ["project", "list"])
+        if result.exit_code != 0:
+            print(f"STDOUT: {result.stdout}")
+            print(f"STDERR: {result.stderr}")
+        assert result.exit_code == 0
+
+        # The removed project should NOT be in the list
+        assert "test-project" not in result.stdout
+        # The new project should be there and marked as default
+        assert "newmain" in result.stdout