replace global flags singleton with Parse() returning Config value

Remove the global atomic.Pointer[Config], sync.Once, and parseErr fields
from the flags package. Parse() now returns (Config, error) directly,
eliminating all global-state accessors (Get, SetPidFilter, SetTidFilter,
SetTUIExportEnable, setCurrent, updateCurrent). The internal parse logic
is factored into parseFromFlagSet so tests can inject a fresh FlagSet
without touching os.Args or package-level state.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/cmd/ior/main.go b/cmd/ior/main.go
index 9c5bac1..d6326cc 100644
--- a/cmd/ior/main.go
+++ b/cmd/ior/main.go
@@ -18,15 +18,14 @@ func main() {
 		os.Exit(2)
 	}
 
-	// Parse command-line flags
-	if err := flags.Parse(); err != nil {
+	// Parse command-line flags; Parse returns the Config directly so there is no
+	// global singleton to read from after this point.
+	cfg, err := flags.Parse()
+	if err != nil {
 		fmt.Printf("Failed to parse flags: %v\n", err)
 		os.Exit(2)
 	}
 
-	// flags.Get() is called here at the CLI boundary so internal code never reads the singleton.
-	cfg := flags.Get()
-
 	// Handle -version: print the banner plus version and exit.
 	if cfg.ShowVersion {
 		flags.PrintVersion()