fix(auth): always show login URL so headless login can complete (#420)

On a machine with no display (e.g. an SSH'd server), login hung and
timed out after 5 minutes. hasBrowser() returned true because xdg-open
was installed, so browser.OpenURL was called; xdg-open printed "no
DISPLAY environment variable specified" to stderr but exited 0, so
OpenURL returned nil and the CLI printed "Waiting for login to complete
in browser..." without ever showing the login URL. With no URL to visit,
login could never complete.

Follow Claude Code's pattern: always attempt to open the browser
best-effort, but always print the login URL as a fallback so the user is
never stranded. Discard the launcher's stderr (pkg/browser pipes it to
ours) to suppress the confusing "no DISPLAY" noise. This removes the need
for platform/display detection, so hasBrowser() is deleted.

Author: theFong

pkg/auth/auth.go

@@ -4,9 +4,8 @@ import (
 	"bufio"
 	"errors"
 	"fmt"
+	"io"
 	"os"
-	"os/exec"
-	"runtime"
 	"strings"
 
 	"github.com/brevdev/brev-cli/pkg/config"
@@ -324,10 +323,20 @@ func (t Auth) LoginWithAPIKey(apiKey string, orgID string) error {
 	return nil
 }
 
-// showLoginURL displays the login link and CLI alternative for manual navigation.
+func init() {
+	// pkg/browser pipes the launcher's stderr to ours, which leaks confusing
+	// noise like "xdg-open: no DISPLAY environment variable specified" on
+	// headless machines. We always print the login URL, so discard it.
+	browser.Stderr = io.Discard
+}
+
+// showLoginURL prints the login link, framed as a fallback for when the
+// browser doesn't open (e.g. headless machine, wrong default browser).
 func showLoginURL(url string) {
 	urlType := color.New(color.FgCyan, color.Bold).SprintFunc()
-	fmt.Println("Login here: " + urlType(url))
+	fmt.Println("Browser didn't open? Use the URL below to sign in:")
+	fmt.Println()
+	fmt.Println(urlType(url))
 }
 
 func defaultAuthFunc(url, code string) {
@@ -337,12 +346,9 @@ func defaultAuthFunc(url, code string) {
 		fmt.Print("\n")
 	}
 
-	if hasBrowser() {
-		if err := browser.OpenURL(url); err == nil {
-			fmt.Println("Waiting for login to complete in browser...")
-			return
-		}
-	}
+	// Best-effort: try to open the browser, but always show the URL below so
+	// the user is never stranded if it doesn't open.
+	_ = browser.OpenURL(url)
 	showLoginURL(url)
 	fmt.Println("\nWaiting for login to complete...")
 }
@@ -352,21 +358,6 @@ func skipBrowserAuthFunc(url, _ string) {
 	fmt.Println("\nWaiting for login to complete...")
 }
 
-// hasBrowser reports whether a browser can be opened on the current platform.
-func hasBrowser() bool {
-	if runtime.GOOS == "darwin" {
-		// macOS always has "open".
-		return true
-	}
-	// Linux: check for a known browser launcher.
-	for _, name := range []string{"xdg-open", "x-www-browser", "www-browser"} {
-		if _, err := exec.LookPath(name); err == nil {
-			return true
-		}
-	}
-	return false
-}
-
 func (t Auth) Login(skipBrowser bool) (*LoginTokens, error) {
 	authFunc := defaultAuthFunc
 	if skipBrowser {