feat: --clear-data flag + typed attribute selectors (#48)

* feat(test): add --clear-data flag to clear app data on launch

* test+docs: cover --clear-data flag in CLI parser test and reference

* feat(spec): type AttrSelector with known attribute names

Replace AttrSelector = Record<string, string> with KnownAttrSelectors
plus a string|boolean index signature, so authors get autocomplete and
type-checking on testTag / focused / clickable / etc. while raw driver
attributes still type-check via the fallback. Boolean state attributes
accept native booleans; goja stringifies them at the marshal boundary.

AccessibilityElement.attrs becomes RawAttrs (typed string-valued shape
of the same canonical names) so element.attrs.testTag autocompletes.

* test(verifier): native boolean selector value matches focused=true

* docs+folio: use native boolean for focused selector and document typed attrs

internal/testrun/testrun.go

@@ -29,6 +29,7 @@ type Options struct {
 	Duration  time.Duration
 	Seed      int64
 	Output    string
+	ClearData bool
 }
 
 // Execute runs the full test pipeline: bundle, launch app, verify properties.
@@ -68,7 +69,7 @@ func Execute(ctx context.Context, options Options, stdout io.Writer) error {
 	}
 	defer cleanup()
 
-	if err := activeDriver.Launch(ctx, options.BundleID, false, nil); err != nil {
+	if err := activeDriver.Launch(ctx, options.BundleID, options.ClearData, nil); err != nil {
 		return fmt.Errorf("launch app: %w", err)
 	}