Add Clide project structure and initial implementation

Set up the TUI IDE wrapper for Claude Code CLI with:
- Core app structure using Textual framework
- Panel architecture (sidebar, workspace, claude, context)
- Theme system with 22 built-in themes (Summer Night default)
- Pydantic models for configuration and data
- Makefile for development commands
- Project documentation and specs

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/harnesses/__init__.py

@@ -0,0 +1,6 @@
+"""Test harnesses for Clide testing."""
+
+from tests.harnesses.app_harness import AppHarness
+from tests.harnesses.controller_harness import ControllerHarness
+
+__all__ = ["AppHarness", "ControllerHarness"]