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

pkg/spec/src/index.ts

@@ -3,15 +3,18 @@ export type {
   AccessibilityTree,
   Action,
   ActionGenerator,
+  AttrSelector,
   EventuallyFormula,
   ExceptionRecord,
   Extracted,
   Formula,
   InputTextAction,
   Key,
+  KnownAttrSelectors,
   LogEntry,
   Point,
   PressKeyAction,
+  RawAttrs,
   Sampler,
   SelectorPath,
   Snapshots,