enforce gofmt formatting and add Fmt/FmtCheck mage targets

Run gofmt -w on 9 files that had minor alignment/whitespace drift
(pair.go, filter.go, ior_mode_registry.go, ior_mode_test.go,
runtime.go, engine.go, dashboard/model.go, flamegraph/model.go,
flamegraph/renderer.go).

Add two new Mage targets to Magefile.go:
- `mage fmt`      – rewrites all .go files in-place via go/format
- `mage fmtCheck` – dry-run check; fails with a list of offending
                    files, suitable as a CI gate

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

1 files changed, 6 insertions, 6 deletions

diff --git a/internal/ior_mode_test.go b/internal/ior_mode_test.go
index 5ba2894..81fd314 100644
--- a/internal/ior_mode_test.go
+++ b/internal/ior_mode_test.go
@@ -31,12 +31,12 @@ import (
 // updating every test.
 func stubDeps() runnerDeps {
 	return runnerDeps{
-		getEUID:             func() int { return 0 },
-		runTrace:            func(flags.Config) error { return nil },
-		runParquet:          func(flags.Config) error { return nil },
-		runTraceWithContext: func(context.Context, flags.Config, chan<- struct{}, func(*eventLoop)) error { return nil },
-		runTUI:              func(flags.Config, runtime.TraceStarter) error { return nil },
-		runTUITestFlames:    func(flags.Config, runtime.TraceStarter) error { return nil },
+		getEUID:              func() int { return 0 },
+		runTrace:             func(flags.Config) error { return nil },
+		runParquet:           func(flags.Config) error { return nil },
+		runTraceWithContext:  func(context.Context, flags.Config, chan<- struct{}, func(*eventLoop)) error { return nil },
+		runTUI:               func(flags.Config, runtime.TraceStarter) error { return nil },
+		runTUITestFlames:     func(flags.Config, runtime.TraceStarter) error { return nil },
 		runTUITestLiveFlames: func(flags.Config, runtime.TraceStarter) error { return nil },
 	}
 }