perf: use batch brew install with native parallelism for CLI packages

Replaces the custom parallel worker pool with a simpler batch install
approach that leverages Homebrew's native parallel download capability
(introduced in Homebrew/brew#20975).

Changes:
- CLI packages are now installed in a single batch: brew install pkg1 pkg2 pkg3...
- Removes 78 lines of complex worker pool code
- Casks remain sequential due to TTY/password prompt requirements
- Dry-run now shows the actual batch command

This aligns with modern Homebrew's HOMEBREW_DOWNLOAD_CONCURRENCY=auto
(default since Nov 2025) which handles parallel downloads automatically.

Author: Jerry Xie

internal/brew/brew.go

@@ -16,8 +16,6 @@ import (
 	"github.com/openbootdotdev/openboot/internal/ui"
 )
 
-const maxWorkers = 1
-
 type OutdatedPackage struct {
 	Name    string
 	Current string
@@ -208,8 +206,8 @@ func InstallWithProgress(cliPkgs, caskPkgs []string, dryRun bool) (installedForm
 
 	if dryRun {
 		ui.Info("Would install packages:")
-		for _, p := range cliPkgs {
-			fmt.Printf("    brew install %s\n", p)
+		if len(cliPkgs) > 0 {
+			fmt.Printf("    brew install %s\n", strings.Join(cliPkgs, " "))
 		}
 		for _, p := range caskPkgs {
 			fmt.Printf("    brew install --cask %s\n", p)
@@ -261,17 +259,29 @@ func InstallWithProgress(cliPkgs, caskPkgs []string, dryRun bool) (installedForm
 	var allFailed []failedJob
 
 	if len(newCli) > 0 {
-		failed := runParallelInstallWithProgress(newCli, progress)
-		failedSet := make(map[string]bool, len(failed))
-		for _, f := range failed {
-			failedSet[f.name] = true
-		}
-		for _, p := range newCli {
-			if !failedSet[p] {
-				installedFormulae = append(installedFormulae, p)
+		progress.SetCurrent(fmt.Sprintf("Installing %d CLI packages...", len(newCli)))
+		ui.Info(fmt.Sprintf("Installing %d CLI packages with native brew parallelism...", len(newCli)))
+		
+		args := append([]string{"install"}, newCli...)
+		cmd := brewInstallCmd(args...)
+		output, err := cmd.CombinedOutput()
+		outputStr := string(output)
+		
+		for _, pkg := range newCli {
+			progress.IncrementWithStatus(true)
+			if err == nil || !strings.Contains(outputStr, pkg) {
+				installedFormulae = append(installedFormulae, pkg)
+			} else {
+				errMsg := parseBrewError(outputStr)
+				if errMsg == "" {
+					errMsg = "install failed"
+				}
+				allFailed = append(allFailed, failedJob{
+					installJob: installJob{name: pkg, isCask: false},
+					errMsg:     errMsg,
+				})
 			}
 		}
-		allFailed = append(allFailed, failed...)
 	}
 
 	if len(newCask) > 0 {
@@ -366,71 +376,6 @@ type failedJob struct {
 	errMsg string
 }
 
-func runParallelInstallWithProgress(pkgs []string, progress *ui.StickyProgress) []failedJob {
-	if len(pkgs) == 0 {
-		return nil
-	}
-
-	jobs := make([]installJob, 0, len(pkgs))
-	for _, pkg := range pkgs {
-		jobs = append(jobs, installJob{name: pkg, isCask: false})
-	}
-
-	jobChan := make(chan installJob, len(jobs))
-	results := make(chan installResult, len(jobs))
-
-	var wg sync.WaitGroup
-	workers := maxWorkers
-	if len(jobs) < workers {
-		workers = len(jobs)
-	}
-
-	for i := 0; i < workers; i++ {
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
-			for job := range jobChan {
-				progress.SetCurrent(job.name)
-				start := time.Now()
-				errMsg := installFormulaWithError(job.name)
-				elapsed := time.Since(start)
-				progress.IncrementWithStatus(errMsg == "")
-				duration := ui.FormatDuration(elapsed)
-				if errMsg == "" {
-					progress.PrintLine("  %s %s", ui.Green("✔ "+job.name), ui.Cyan("("+duration+")"))
-				} else {
-					progress.PrintLine("  %s %s", ui.Red("✗ "+job.name+" ("+errMsg+")"), ui.Cyan("("+duration+")"))
-				}
-				results <- installResult{name: job.name, failed: errMsg != "", isCask: job.isCask, errMsg: errMsg}
-			}
-		}()
-	}
-
-	go func() {
-		for _, job := range jobs {
-			jobChan <- job
-		}
-		close(jobChan)
-	}()
-
-	go func() {
-		wg.Wait()
-		close(results)
-	}()
-
-	var failed []failedJob
-	for result := range results {
-		if result.failed {
-			failed = append(failed, failedJob{
-				installJob: installJob{name: result.name, isCask: result.isCask},
-				errMsg:     result.errMsg,
-			})
-		}
-	}
-
-	return failed
-}
-
 func installCaskWithProgress(pkg string, progress *ui.StickyProgress) string {
 	progress.PauseForInteractive()