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/conftest.py

@@ -0,0 +1,81 @@
+"""Shared pytest fixtures for Clide tests."""
+
+from pathlib import Path
+from typing import AsyncGenerator, Generator
+from unittest.mock import MagicMock
+
+import pytest
+from textual.pilot import Pilot
+
+from clide.app import ClideApp
+from clide.extensions.manager import ExtensionManager
+from clide.models.config import ClideSettings
+from tests.harnesses.app_harness import AppHarness
+from tests.harnesses.controller_harness import ControllerHarness
+
+
+@pytest.fixture
+def temp_workdir(tmp_path: Path) -> Path:
+    """Create a temporary working directory with sample files."""
+    # Create sample directory structure
+    (tmp_path / "src").mkdir()
+    (tmp_path / "tests").mkdir()
+    (tmp_path / "src" / "main.py").write_text("# Main file")
+    (tmp_path / "README.md").write_text("# Test Project")
+
+    # Initialize git repo
+    (tmp_path / ".git").mkdir()
+
+    return tmp_path
+
+
+@pytest.fixture
+def mock_settings() -> ClideSettings:
+    """Create test settings with defaults."""
+    return ClideSettings(
+        theme="dark",
+        claude_path="/usr/bin/echo",  # Safe mock
+        auto_save=False,
+        confirm_exit=False,
+    )
+
+
+@pytest.fixture
+def mock_extension_manager() -> ExtensionManager:
+    """Create an extension manager without loading external extensions."""
+    manager = ExtensionManager()
+    # Don't load entry points in tests
+    return manager
+
+
+@pytest.fixture
+def app_harness(
+    temp_workdir: Path,
+    mock_settings: ClideSettings,
+    mock_extension_manager: ExtensionManager,
+) -> Generator[AppHarness, None, None]:
+    """Create a full application test harness."""
+    harness = AppHarness(
+        workdir=temp_workdir,
+        settings=mock_settings,
+        extension_manager=mock_extension_manager,
+    )
+    yield harness
+
+
+@pytest.fixture
+async def running_app(
+    app_harness: AppHarness,
+) -> AsyncGenerator[tuple[ClideApp, Pilot], None]:
+    """Start the app and yield (app, pilot) for interaction."""
+    app, pilot = await app_harness.start()
+    try:
+        yield app, pilot
+    finally:
+        await app_harness.stop()
+
+
+@pytest.fixture
+def controller_harness() -> ControllerHarness:
+    """Create an isolated controller test harness."""
+    return ControllerHarness()