fix(ios-prebuild): flow strict-local + prettier cleanup for the compose guard test

new Set() needed an explicit type argument under strict-local, and the
exec-in-while-condition loop lost Flow's null refinement — matchAll avoids
both. headers-rules.md reflowed by prettier.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: chrfalch

packages/react-native/scripts/ios-prebuild/__docs__/headers-rules.md

@@ -361,9 +361,9 @@ the other third-party deps namespaces, with a single physical home in the
 ReactNativeDependenciesHeaders sidecar: relocating a second textual copy into
 ReactNativeHeaders collided with the real pod's own headers under
 `use_frameworks` (the duplicate-`@interface` / poisoned-module-graph Expo
-regression, 2026-07-03), so the set-equality gate asserts the declared
-namespace set — `DEPS_NAMESPACES` — matches the deps artifact's namespaces
-exactly, in both directions.
+regression, 2026-07-03), so the set-equality gate asserts the declared namespace
+set — `DEPS_NAMESPACES` — matches the deps artifact's namespaces exactly, in
+both directions.
 
 ### D. Remaining silent gaps — allowlist maintenance (by design)
 

packages/react-native/scripts/ios-prebuild/__tests__/headers-compose-test.js

@@ -24,9 +24,8 @@ describe('COMPOSE_TOOLING_FILES stays in sync with headers-compose.js requires',
       'utf8',
     );
     const requireRe = /require\('\.\/([\w-]+)'\)/g;
-    const required = new Set();
-    let match;
-    while ((match = requireRe.exec(source)) != null) {
+    const required = new Set<string>();
+    for (const match of source.matchAll(requireRe)) {
       required.add(`${match[1]}.js`);
     }
     for (const name of required) {