vendor-hermes: advance the pin past Hermes' JSI_UNSTABLE default flip

The Android test app crashed on startup, in `NodeApiHostPackage.<init>`:

    java.lang.UnsatisfiedLinkError: dlopen failed: cannot locate symbol
    "_ZTIN8facebook3jsi10SerializedE" referenced by ".../libhermesvm.so"
    com.facebook.soloader.SoLoaderDSONotFoundError: couldn't find DSO to
    load: libhermesvm.so

That symbol is `typeinfo for facebook::jsi::Serialized`. JSI's
`Serialized` / `ISerialization` APIs sit behind `#ifdef JSI_UNSTABLE`,
and React Native never defines it when building the `libjsi.so` it ships
in the ReactAndroid AAR. Our pinned Hermes still defaulted `JSI_UNSTABLE`
to ON, so `hermesvm` compiled those APIs in and referenced symbols that
nothing in the APK defines.

Apple builds are unaffected because JSI is compiled into the `hermesvm`
framework itself; on Android the two are separate shared libraries, and
RN's hermes-engine build imports `libjsi.so` rather than packaging the
copy Hermes builds for itself.

facebook/hermes 5a795c9f8 ("Fix: JSI_UNSTABLE CMake flag should be OFF by
default") is the immediate child of the previous pin, so this picks up
the one-line fix and nothing else.

Verified by rebuilding the release APK for x86_64: `libhermesvm.so` no
longer references `jsi::Serialized`, and every undefined JSI symbol it
does have is defined by a library shipped in the APK.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: kraenhansen

packages/host/src/node/cli/hermes.ts

@@ -30,7 +30,16 @@ const HERMES_GIT_URL = "https://github.com/facebook/hermes.git";
 // framework hit "Undefined symbol: hermes_napi_create_env". We used to patch
 // the header ourselves after cloning; now that the fix is upstream at this pin,
 // no header patching is required.
-const HERMES_GIT_SHA = "efcf68e285865fd9d952070b08e751bcad63f25e";
+//
+// It also includes the immediately following commit, which flips Hermes'
+// `JSI_UNSTABLE` CMake flag back to OFF by default. With it ON, Hermes compiles
+// JSI's unstable `Serialized` / `ISerialization` APIs into `hermesvm`, but
+// React Native never defines `JSI_UNSTABLE` when building the `libjsi.so` it
+// ships in the ReactAndroid AAR. On Android the two are separate shared
+// libraries, so `libhermesvm.so` ended up with undefined references to
+// `facebook::jsi::Serialized` that nothing in the APK defined, and the app died
+// on startup with "cannot locate symbol _ZTIN8facebook3jsi10SerializedE".
+const HERMES_GIT_SHA = "5a795c9f880002c862c9254a26b57199819c97f7";
 
 const platformOption = new Option(
   "--react-native-package <package-name>",