refactor: reorganize into monorepo with separate subprojects

Structure webber into three independent subprojects:
- webber-api/: FastAPI backend server with all agent code
- webber-cli/: Standalone CLI client (renamed from cli/ to webber_cli/)
- webber-sandbox/: Test project for functional testing

Key changes:
- Each subproject has its own .venv (Python 3.12+)
- Added sandbox.sh for managing test project templates
- Created sandbox-templates/ with calculator-cli and empty starter
- Updated CI/CD for prefixed tags (api/v*, cli/v*)
- Added comprehensive AGENTS.md with operational instructions
- Added gitignore filtering to glob and grep tools
- Created pyproject.toml for each subproject

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

webber-api/src/cli/theme.py

@@ -0,0 +1,70 @@
+"""
+CLI theme configuration.
+
+Centralized color and style definitions for the Webber CLI.
+All color choices should be defined here for easy customization.
+"""
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class ThemeColors:
+    """Color palette for the CLI."""
+
+    # Semantic colors
+    info: str = "steel_blue"
+    warning: str = "dark_orange"
+    error: str = "red3"
+    success: str = "sea_green3"
+
+    # UI elements
+    prompt: str = "steel_blue bold"
+    title: str = "steel_blue bold"
+    path: str = "steel_blue underline"
+    code: str = "sea_green3"
+    highlight: str = "medium_purple1"
+    dim: str = "dim white"
+
+    # Panel borders
+    border_default: str = "steel_blue"
+    border_success: str = "sea_green3"
+    border_error: str = "red3"
+    border_warning: str = "dark_orange"
+
+
+@dataclass(frozen=True)
+class ThemeConfig:
+    """Complete theme configuration."""
+
+    colors: ThemeColors = ThemeColors()
+
+    # Spinner style for loading indicators
+    spinner: str = "dots"
+
+    # Code syntax highlighting theme
+    syntax_theme: str = "monokai"
+
+    def to_rich_theme_dict(self) -> dict[str, str]:
+        """Convert to Rich theme dictionary."""
+        return {
+            "info": self.colors.info,
+            "warning": self.colors.warning,
+            "error": self.colors.error,
+            "success": self.colors.success,
+            "prompt": self.colors.prompt,
+            "title": self.colors.title,
+            "path": self.colors.path,
+            "code": self.colors.code,
+            "highlight": self.colors.highlight,
+            "dim": self.colors.dim,
+        }
+
+
+# Default theme instance
+DEFAULT_THEME = ThemeConfig()
+
+
+def get_theme() -> ThemeConfig:
+    """Get the current theme configuration."""
+    # Future: could load from config file or env vars
+    return DEFAULT_THEME