refactor: pass flags.Config explicitly, remove flags.Get() from library code (task 429)

flags.Get() (global mutable singleton) was called inside library packages,
coupling them to global state and making tests fragile (DIP violation).

- internal.Run() now takes an explicit flags.Config; main.go calls
  flags.Get() once at the CLI boundary and passes it in.
- tui.Run(), RunWithTraceStarter(), RunTestFlamesWithTraceStarter() removed;
  callers already used the WithConfig variants directly.
- tui.NewModel() preserved for test ergonomics but now uses flags.NewFlags()
  (pure defaults) instead of flags.Get() (global state).
- Tests updated to use NewModelWithConfig() with explicit config structs
  instead of flags.Set*() + NewModel(), eliminating all test-level
  global-state mutation.

flags.Get() is now called only in cmd/ior/main.go, the correct boundary.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/cmd/ior/main.go b/cmd/ior/main.go
index 2b852f0..8d93d28 100644
--- a/cmd/ior/main.go
+++ b/cmd/ior/main.go
@@ -23,8 +23,9 @@ func main() {
 		os.Exit(2)
 	}
 
-	// Run the internal logic of the application
-	if err := internal.Run(); err != nil {
+	// Run the internal logic of the application.
+	// flags.Get() is called here at the CLI boundary so internal code never reads the singleton.
+	if err := internal.Run(flags.Get()); err != nil {
 		fmt.Printf("Failed to run: %v\n", err)
 		os.Exit(2)
 	}