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/package.json

@@ -14,7 +14,8 @@
 	],
 	"scripts": {
 		"clean": "rm -rf dist",
-		"build": "tsgo -p tsconfig.build.json && chmod +x dist/cli.js",
+		"build": "tsgo -p tsconfig.build.json && chmod +x dist/cli.js && npm run copy-theme-assets",
+		"copy-theme-assets": "cp src/theme/*.json dist/theme/",
 		"dev": "tsgo -p tsconfig.build.json --watch --preserveWatchOutput",
 		"check": "tsgo --noEmit",
 		"test": "vitest --run",