feat: add multi-engine regex flavour support

src/components/HelpDialog.tsx

@@ -48,13 +48,24 @@ export function HelpDialog({
           <h3>What runs where</h3>
           <p>
             Syntax parsing and active-engine execution run in separate, killable
-            browser workers. ECMAScript uses the browser RegExp implementation;
-            PCRE2 uses the bundled 10.47 WebAssembly engine; Python uses CPython
-            3.14 through Pyodide; and Java uses TeaVM&apos;s java.util.regex
-            compatibility implementation. The result metadata names the runtime
-            actually used. Patterns, subjects and projects are never uploaded.
-            There is no backend, account, telemetry, CDN dependency, or
-            executable replacement function.
+            browser workers. JavaScript uses the browser&apos;s ECMAScript
+            RegExp implementation, while the standalone PCRE2 profile uses the
+            bundled 10.47 WebAssembly engine. The other profiles name their
+            selected runtime explicitly: PHP 8.5.8 preg with PCRE2 10.44, legacy
+            Perl 5.28.1 through WebPerl 0.09-beta, CPython 3.14, CRuby 4.0,
+            TeaVM java.util.regex, libc++ std::regex, Go regexp, Rust regex and
+            .NET System.Text.RegularExpressions. Scala is explicitly a Scala/JVM
+            regex-syntax compatibility profile over the same TeaVM Java runtime,
+            not a Scala VM. Result metadata names the runtime actually used.
+          </p>
+          <p>
+            Structural coverage varies by profile. Only the ECMAScript provider
+            currently exposes a complete grammar-backed tree; the additional
+            community providers retain partial lexical captures and replacement
+            tokens while their selected runtime compiler remains authoritative.
+            Patterns, subjects and projects are never uploaded. There is no
+            backend, account, telemetry, CDN dependency, or executable
+            replacement function.
           </p>
           <p>
             TeaVM 0.15.0 is not OpenJDK. Its replacement implementation accepts