Remove unreachable back button handler in IOSDriver.press_button()
(guard rejects it before reaching the handler). Guard empty
supported_buttons producing malformed system_button description.
Update iOS docs to match current driver behavior: get_date() works,
input_text() clear is supported, swipe uses coordinates, port is 6643.
Replace stub iOS setup guide with full Xcode build/signing/iproxy
instructions.
Remove v3, v4, and v5 directories. Move latest (v5) docs to docs root.
Update docs.json navigation to use flat tabs instead of versioned layout.
Fix all internal links to use unversioned paths.
Move all root-level doc pages (overview, quickstart, features, concepts,
guides, sdk) into docs/v4/ to match the versioning pattern used by
v1/v2/v3. Update docs.json navigation and all internal cross-references
to use /v4/ prefix. Fix broken anchor link in app-cards.mdx.