WIP: Add theming system with /theme command

- Consolidated theme system into single src/theme/ directory
- Created Theme class with fg(), bg(), bold(), italic(), underline()
- Added dark and light built-in themes with 36 color tokens
- Support for custom themes in ~/.pi/agent/themes/*.json
- JSON schema for theme validation
- Theme selector UI with /theme command
- Save theme preference to settings
- Uses chalk for text formatting to preserve colors

TODO:
- Replace hardcoded colors throughout TUI components
- Apply markdown theming to Markdown components
- Add theme support to all TUI elements

packages/coding-agent/src/main.ts

@@ -10,6 +10,7 @@ import { getChangelogPath, getNewEntries, parseChangelog } from "./changelog.js"
 import { findModel, getApiKeyForModel, getAvailableModels } from "./model-config.js";
 import { SessionManager } from "./session-manager.js";
 import { SettingsManager } from "./settings-manager.js";
+import { initTheme } from "./theme/theme.js";
 import { codingTools } from "./tools/index.js";
 import { SessionSelectorComponent } from "./tui/session-selector.js";
 import { TuiRenderer } from "./tui/tui-renderer.js";
@@ -563,6 +564,11 @@ export async function main(args: string[]) {
 		return;
 	}
 
+	// Initialize theme (before any TUI rendering)
+	const settingsManager = new SettingsManager();
+	const themeName = settingsManager.getTheme();
+	initTheme(themeName);
+
 	// Setup session manager
 	const sessionManager = new SessionManager(parsed.continue && !parsed.resume, parsed.session);
 
@@ -582,9 +588,6 @@ export async function main(args: string[]) {
 		sessionManager.setSessionFile(selectedSession);
 	}
 
-	// Settings manager
-	const settingsManager = new SettingsManager();
-
 	// Determine initial model using priority system:
 	// 1. CLI args (--provider and --model)
 	// 2. Restored from session (if --continue or --resume)