keyboard: fix interactive dismiss race conditions, rewrite example

Fix several race conditions in the iOS interactive dismiss flow:
- Don't skip keyboard close notifications during pan tracking, which
  left Dart unaware the keyboard was dismissed
- Guard resignFirstResponder with generation check so reopened keyboards
  aren't killed by stale dismiss completions
- Block pan tracking from starting during an in-flight dismiss animation
- Always reset keyboard view bounds when the keyboard opens, not just
  when the dismiss animator is still running
- Handle duration=0 keyboard notifications by snapping immediately
- Gate adaptive learning debug output behind kDebugMode

Rewrite the example as a chat UI demonstrating ListenableBuilder,
scroll freeze during interactive dismiss, and proper bottom inset
handling with max(keyboardHeight, safeBottom).

Modernize example Android project from v1 to v2 embedding with
current AGP/Gradle versions.

example/ios/Podfile

@@ -1,5 +1,5 @@
 # Uncomment this line to define a global platform for your project
-# platform :ios, '9.0'
+# platform :ios, '13.0'
 
 # CocoaPods analytics sends network stats synchronously affecting flutter build latency.
 ENV['COCOAPODS_DISABLE_STATS'] = 'true'
@@ -10,63 +10,31 @@ project 'Runner', {
   'Release' => :release,
 }
 
-def parse_KV_file(file, separator='=')
-  file_abs_path = File.expand_path(file)
-  if !File.exists? file_abs_path
-    return [];
+def flutter_root
+  generated_xcode_build_settings_path = File.expand_path(File.join('..', 'Flutter', 'Generated.xcconfig'), __FILE__)
+  unless File.exist?(generated_xcode_build_settings_path)
+    raise "#{generated_xcode_build_settings_path} must exist. If you're running pod install manually, make sure flutter pub get is executed first"
   end
-  pods_ary = []
-  skip_line_start_symbols = ["#", "/"]
-  File.foreach(file_abs_path) { |line|
-      next if skip_line_start_symbols.any? { |symbol| line =~ /^\s*#{symbol}/ }
-      plugin = line.split(pattern=separator)
-      if plugin.length == 2
-        podname = plugin[0].strip()
-        path = plugin[1].strip()
-        podpath = File.expand_path("#{path}", file_abs_path)
-        pods_ary.push({:name => podname, :path => podpath});
-      else
-        puts "Invalid plugin specification: #{line}"
-      end
-  }
-  return pods_ary
+
+  File.foreach(generated_xcode_build_settings_path) do |line|
+    matches = line.match(/FLUTTER_ROOT\=(.*)/)
+    return matches[1].strip if matches
+  end
+  raise "FLUTTER_ROOT not found in #{generated_xcode_build_settings_path}. Try deleting Generated.xcconfig, then run flutter pub get"
 end
 
+require File.expand_path(File.join('packages', 'flutter_tools', 'bin', 'podhelper'), flutter_root)
+
+flutter_ios_podfile_setup
+
 target 'Runner' do
-  # Prepare symlinks folder. We use symlinks to avoid having Podfile.lock
-  # referring to absolute paths on developers' machines.
-  system('rm -rf .symlinks')
-  system('mkdir -p .symlinks/plugins')
+  use_frameworks!
 
-  # Flutter Pods
-  generated_xcode_build_settings = parse_KV_file('./Flutter/Generated.xcconfig')
-  if generated_xcode_build_settings.empty?
-    puts "Generated.xcconfig must exist. If you're running pod install manually, make sure flutter pub get is executed first."
-  end
-  generated_xcode_build_settings.map { |p|
-    if p[:name] == 'FLUTTER_FRAMEWORK_DIR'
-      symlink = File.join('.symlinks', 'flutter')
-      File.symlink(File.dirname(p[:path]), symlink)
-      pod 'Flutter', :path => File.join(symlink, File.basename(p[:path]))
-    end
-  }
-
-  # Plugin Pods
-  plugin_pods = parse_KV_file('../.flutter-plugins')
-  plugin_pods.map { |p|
-    symlink = File.join('.symlinks', 'plugins', p[:name])
-    File.symlink(p[:path], symlink)
-    pod p[:name], :path => File.join(symlink, 'ios')
-  }
+  flutter_install_all_ios_pods File.dirname(File.realpath(__FILE__))
 end
 
-# Prevent Cocoapods from embedding a second Flutter framework and causing an error with the new Xcode build system.
-install! 'cocoapods', :disable_input_output_paths => true
-
 post_install do |installer|
   installer.pods_project.targets.each do |target|
-    target.build_configurations.each do |config|
-      config.build_settings['ENABLE_BITCODE'] = 'NO'
-    end
+    flutter_additional_ios_build_settings(target)
   end
 end