auto-update: drop confirmation dialog, do it silently

Chrome-style silent updater: no prompt, no progress UI, no buttons.
On startup we check for updates (8s timeout), and if one is found
we download + verify + apply + relaunch — total ~3-5s on a fast
connection. The user sees the new version's window instead of the
old one, period.

Errors that do warrant a dialog (apply failed mid-write, sha256
mismatch, can't relaunch) still surface as a message box so the
user knows their copy is on the previous version. 'No update' and
network timeouts stay silent.

Split timeouts so a 60s download doesn't get killed by the 8s
check budget.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/drover/autoupdate_windows.go

@@ -14,32 +14,35 @@ import (
 	"golang.org/x/sys/windows"
 )
 
-// autoUpdateOnStartup runs a non-interactive update check whenever drover.exe
-// starts as a GUI app (no CLI subcommand). If an update is available, a
-// Yes/No message box prompts the user; on Yes we download, verify, apply
-// the update, then re-launch the binary so the new version is what they see.
+// autoUpdateOnStartup silently checks for and applies updates whenever
+// drover.exe starts as a GUI app (no CLI subcommand). Chrome-style: no
+// prompt, no progress bar, no questions — if an update is available we
+// download, verify, apply, and re-launch. The user just sees the new
+// version's window appear instead of the old one.
 //
-// Network failures, server outages, and "no updates available" are silent
-// fall-throughs — startup must never block on them.
+// Network failures, server outages, slow downloads, and "no updates
+// available" are silent fall-throughs — startup must never block on them.
+//
+// Two split contexts:
+//   - check  (8s)  — quick HEAD-equivalent against the releases API
+//   - apply (60s)  — actual download + sha256 + atomic replace
 func autoUpdateOnStartup() {
-	// Tight timeout — startup, not a long-running task.
-	ctx, cancel := context.WithTimeout(context.Background(), 8*time.Second)
-	defer cancel()
-
 	src := updater.NewForgejoSource("git.okcu.io", "root", "drover-go", "windows-amd64.exe")
-	rel, hasUpdate, err := updater.CheckForUpdate(ctx, src, Version)
+
+	checkCtx, cancelCheck := context.WithTimeout(context.Background(), 8*time.Second)
+	rel, hasUpdate, err := updater.CheckForUpdate(checkCtx, src, Version)
+	cancelCheck()
 	if err != nil || !hasUpdate {
-		// Silent: offline, slow network, or already up to date — none of
-		// these should interrupt the user.
 		return
 	}
 
-	if !confirmUpdateDialog(rel) {
-		return
-	}
-
-	if err := updater.ApplyUpdate(ctx, rel, nil); err != nil {
-		errorDialog(fmt.Sprintf("Update failed: %v", err))
+	applyCtx, cancelApply := context.WithTimeout(context.Background(), 60*time.Second)
+	defer cancelApply()
+	if err := updater.ApplyUpdate(applyCtx, rel, nil); err != nil {
+		// Apply failed — surface this one (sha mismatch, write error,
+		// disk full are not silent-fail cases). The user can keep using
+		// the current version after dismissing the dialog.
+		errorDialog(fmt.Sprintf("Update to %s failed: %v\n\nContinuing on current version.", rel.TagName, err))
 		return
 	}
 
@@ -48,36 +51,10 @@ func autoUpdateOnStartup() {
 		return
 	}
 
-	// Successfully spawned the new version — exit cleanly so it can take over.
+	// Successfully spawned the new version — exit cleanly so it takes over.
 	os.Exit(0)
 }
 
-// confirmUpdateDialog asks the user whether to apply the available update.
-// Returns true on Yes (IDYES = 6).
-func confirmUpdateDialog(rel *updater.Release) bool {
-	user32 := windows.NewLazySystemDLL("user32.dll")
-	messageBox := user32.NewProc("MessageBoxW")
-
-	body := fmt.Sprintf(
-		"A new version is available.\n\n"+
-			"Current:  v%s\n"+
-			"Latest:   %s\n\n"+
-			"Install it now? Drover-Go will restart automatically.",
-		Version, rel.TagName,
-	)
-	title := "Drover-Go — Update available"
-
-	bodyW, _ := windows.UTF16PtrFromString(body)
-	titleW, _ := windows.UTF16PtrFromString(title)
-
-	// MB_YESNO | MB_ICONQUESTION | MB_SETFOREGROUND | MB_TOPMOST | MB_DEFBUTTON1
-	const flags = 0x00000004 | 0x00000020 | 0x00010000 | 0x00040000 | 0x00000000
-
-	r, _, _ := messageBox.Call(0, uintptr(unsafe.Pointer(bodyW)), uintptr(unsafe.Pointer(titleW)), flags)
-	const IDYES = 6
-	return r == IDYES
-}
-
 func errorDialog(msg string) {
 	user32 := windows.NewLazySystemDLL("user32.dll")
 	messageBox := user32.NewProc("MessageBoxW")