Regex operations return incorrect results when ARM Memory Tagging Extensions (MTE) are enabled

Boost version:
1.90.0. I've also seen this on 1.86.0, and don't think it's specific to any particular Boost version.

Test hardware:
Google Pixel 9

Test OS:
Android 16 QPR3 Beta 2 (build CP11.251209.007.A1).
This build seems to have MTE enabled system-wide by default. Can be verified under Settings>System>Developer options>Memory Tagging Extension.

Description:
Boost regex operation return incorrect results, e.g. `boost::regex_match` returns false in cases when it should return true.
This seems to occur when both of the following are true:
1) Memory Tagging Extensions are enabled.
2) A character type larger than 1 byte (e.g. `wchar_t`) is used.

Steps to reproduce:
I have prepared a minimal reproducible example.
In Android Studio, select New>New project...>Native C++, and complete the wizard.

Then replace the contents of the following files:

app/src/main/cpp/native-lib.cpp
```
#include
#include
#include "boost/regex.hpp"

using CharT = wchar_t;
using String = std::basic_string;

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_boostregex16qpr3b2_MainActivity_stringFromJNI(
JNIEnv* env,
jobject /* this */) {
String input = L"ABC";
String pattern = L"^[A-Z]{1,100}$"; // Note: 99 and below as the upper bound works for some reason.

boost::basic_regex> re;
re.imbue(std::locale::classic());
re.assign(pattern,boost::regex::perl);

if (boost::regex_match(input, re)) {
return env->NewStringUTF("OK");
} else {
return env->NewStringUTF("Fail");
}
}
```

app/src/main/cpp/CMakeLists.txt
```
cmake_minimum_required(VERSION 3.22.1)

project("boostregex16qpr3b2")

set(BOOST_SRC_RELATIVE_PATH "" CACHE STRING "Path to the Boost source code, relative to app/src/main")
get_filename_component(BOOSTSRCROOT ../${BOOST_SRC_RELATIVE_PATH} ABSOLUTE)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

add_library(boost_headers INTERFACE)
target_include_directories(boost_headers INTERFACE ${BOOSTSRCROOT})

add_library(native-lib SHARED
native-lib.cpp
)
target_compile_options(native-lib PUBLIC
-funwind-tables -fomit-frame-pointer
-fno-strict-aliasing
-Wa,--noexecstack
)
target_link_options(native-lib PRIVATE "-Wl,-z,max-page-size=16384")
target_link_libraries(native-lib
boost_headers
android
log)
```

app/build.gradle.kts
```
plugins {
alias(libs.plugins.android.application)
alias(libs.plugins.kotlin.android)
}

android {
namespace = "com.example.boostregex16qpr3b2"
compileSdk {
version = release(36)
}

ndkVersion = "27.3.13750724"

defaultConfig {
applicationId = "com.example.boostregex16qpr3b2"
minSdk = 28
targetSdk = 35
versionCode = 1
versionName = "1.0"

testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
arguments(
"-DBOOST_SRC_RELATIVE_PATH=../../../../../../github/boost_1_90_0"
)
}
}
}

buildTypes {
release {
isMinifyEnabled = false
proguardFiles(
getDefaultProguardFile("proguard-android-optimize.txt"),
"proguard-rules.pro"
)
}
}
compileOptions {
sourceCompatibility = JavaVersion.VERSION_11
targetCompatibility = JavaVersion.VERSION_11
}
kotlinOptions {
jvmTarget = "11"
}
externalNativeBuild {
cmake {
path = file("src/main/cpp/CMakeLists.txt")
version = "3.22.1"
}
}
buildFeatures {
viewBinding = true
}
}

dependencies {
implementation(libs.androidx.core.ktx)
implementation(libs.androidx.appcompat)
implementation(libs.material)
implementation(libs.androidx.constraintlayout)
testImplementation(libs.junit)
androidTestImplementation(libs.androidx.junit)
androidTestImplementation(libs.androidx.espresso.core)
}
```

Running the resulting app on the aforementioned Test device/OS will display "Fail" on the screen, instead of the expected "OK".

Start with app/src/main/cpp/native-lib.cpp and the accompanying CMakeLists.txt, then build and run the minimal example on the Pixel 9 with MTE enabled. Trace the Boost regex path used by wchar_t and the {1,100} pattern, comparing it with the reported {1,99} behavior. Done means the example displays "OK" for the valid match under the affected Android configuration.

Written by the indexing model from the issue text.