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/create-contact.yaml

@@ -0,0 +1,16 @@
+appId: com.google.android.contacts
+name: Create Contact
+---
+- launchApp
+- wait: 2
+- tap: "Create new contact"
+- wait: 1
+- tap: "First name"
+- type: "John"
+- tap: "Last name"
+- type: "Snow"
+- tap: "Phone"
+- type: "5551234567"
+- tap: "Save"
+- wait: 2
+- done: "Contact created"