fix: Xcode 26 compatibility — strip .Swift submodule from RiveRuntime modulemaps (#174)

Fixes #173

RiveRuntime's prebuilt XCFramework was built with Swift 6.1. Xcode 26
uses Swift 6.2. Both generate `.Swift` Clang submodules with different
C++ interop type definitions (`swift::Optional`, `swift::String`, etc),
causing hard ODR errors that can't be suppressed. This is
CocoaPods-specific — SPM is unaffected because it uses `.swiftmodule`
files directly.

The fix hooks into CocoaPods' `pre_install` via `Module#prepend` in the
podspec to strip the `.Swift` submodule from RiveRuntime's prebuilt
modulemaps. This is transparent to users — no Podfile changes needed.

### Modulemap patch

```diff
 framework module RiveRuntime {
   umbrella header "RiveRuntime.h"
   export *

   module * { export * }
 }
-
-module RiveRuntime.Swift {
-  header "RiveRuntime-Swift.h"
-  requires objc
-}
```

### Build error without fix (Xcode 26.2)

```
RiveRuntime-Swift.h:3603:62: error: '(lambda ...)' has different definitions in different modules;
  first difference is definition in module 'RiveRuntime.Swift' found method 'operator()' with body
RiveRuntime-Swift.h:3596:78: error: 'swift::Optional::init' has different definitions in different modules;
  definition in module 'RiveRuntime.Swift' first difference is 1st parameter with name 'some_'
LocalCxxPod-Swift.h:2177:29: error: 'swift::UTF8View' has different definitions in different modules
LocalCxxPod-Swift.h:1984:37: error: 'swift::String' has different definitions in different modules
LocalCxxPod-Swift.h:1722:52: error: 'swift::Optional' has different definitions in different modules;
  first difference is definition in module 'LocalCxxPod.Swift' found method 'init' with 1st parameter named 'value'
```

### After fix

BUILD SUCCEEDED (Xcode 26.2, clean DerivedData, `pod install` +
`xcodebuild`)

Author: mfazekas

RNRive.podspec

@@ -30,6 +30,28 @@ end
 
 Pod::UI.puts "@rive-app/react-native: Rive iOS SDK #{rive_ios_version}"
 
+# Xcode 26 workaround: strip .Swift Clang submodule from RiveRuntime's prebuilt
+# modulemaps to prevent ODR conflicts with locally-compiled Swift C++ interop.
+# See: https://github.com/rive-app/rive-nitro-react-native/issues/173
+if defined?(Pod::Installer)
+  module RiveXcode26SwiftModuleFix
+    def run_podfile_pre_install_hooks
+      rive_dir = File.join(sandbox.root.to_s, 'RiveRuntime')
+      if Dir.exist?(rive_dir)
+        Dir.glob(File.join(rive_dir, '**', 'module.modulemap')).each do |path|
+          content = File.read(path)
+          next unless content.include?('RiveRuntime.Swift')
+          cleaned = content.gsub(/\nmodule RiveRuntime\.Swift \{[^}]*\}\n?/m, "\n")
+          File.write(path, cleaned)
+        end
+      end
+      super
+    end
+  end
+
+  Pod::Installer.prepend(RiveXcode26SwiftModuleFix)
+end
+
 Pod::Spec.new do |s|
   s.name         = "RNRive"
   s.version      = package["version"]