Add Maestro-style YAML flow runner for deterministic automation

New --flow mode executes scripted YAML steps without LLM, mapping 17
commands (tap, type, swipe, scroll, etc.) to existing actions. Element
finding uses accessibility tree text/hint/id matching.

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

examples/flows/google-search.yaml

@@ -0,0 +1,10 @@
+appId: com.google.android.googlequicksearchbox
+name: Google Search
+---
+- launchApp
+- wait: 2
+- tap: "Search"
+- type: "weather today"
+- enter
+- wait: 3
+- done: "Search results loaded"