style(tools): unify console output with [I/W/E] [Module] color-coded format

- Add ANSI color coding: [I]=green, [W]=yellow, [E]=red
- Format: [Level] [Module] message with 4-char indent for data rows
- Error detail lines use |-> tree connector
- Remove extra blank lines between outputs (except list)
- Modules: CLI, Preview, Builder, Server, Watcher

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tools/cli/preview.go

@@ -2,7 +2,6 @@ package cli
 
 import (
 	"fmt"
-	"log"
 	"path/filepath"
 
 	"github.com/urfave/cli/v2"
@@ -78,7 +77,7 @@ func runPreview(c *cli.Context) error {
 
 	preview.PrintDetailedSummary(result, folder, cfg)
 
-	log.Printf("Wrote %d themes x %d templates to %s",
+	fmt.Printf("\033[32m[I]\033[0m [Preview] Wrote %d themes x %d templates to %s\n",
 		len(result.Summaries), len(cfg.Templates), outputPath)
 
 	return nil