Fix memory leak in normalize_language by using Cow instead of Box::leak (#91)

## Summary

- Replace `Box::leak` with `Cow<'_, str>` in `normalize_language` to
avoid memory leaks
- Unknown language names now borrow from input instead of leaking
allocated memory
- Known aliases still return static string references via
`Cow::Borrowed`

Fixes #90

Author: fasterthanlime

xtask/templates/umbrella_store.stpl.rs

@@ -8,6 +8,7 @@
 //! This file is automatically generated from the grammar registry
 //! (`langs/group-*/*/def/arborium.kdl`). Do not edit manually.
 
+use std::borrow::Cow;
 use std::collections::HashMap;
 use std::sync::{Arc, RwLock};
 
@@ -61,37 +62,36 @@ impl GrammarStore {
         // Fast path: check if already cached
         {
             let grammars = self.grammars.read().unwrap();
-            if let Some(grammar) = grammars.get(normalized) {
+            if let Some(grammar) = grammars.get(&*normalized) {
                 return Some(grammar.clone());
             }
         }
 
         // Slow path: compile and cache
-        let grammar = Self::compile_grammar(normalized)?;
+        let grammar = Self::compile_grammar(&normalized)?;
         let grammar = Arc::new(grammar);
 
         {
             let mut grammars = self.grammars.write().unwrap();
             // Double-check in case another thread compiled it
-            if let Some(existing) = grammars.get(normalized) {
+            if let Some(existing) = grammars.get(&*normalized) {
                 return Some(existing.clone());
             }
-            grammars.insert(normalized.to_string(), grammar.clone());
+            grammars.insert(normalized.into_owned(), grammar.clone());
         }
 
         Some(grammar)
     }
 
     /// Normalize a language name to its canonical form.
-    fn normalize_language(language: &str) -> &'static str {
+    fn normalize_language(language: &str) -> Cow<'_, str> {
         match language {
             // Aliases (generated from arborium.kdl)
 <% for (alias, canonical) in aliases { %>
-            "<%= alias %>" => "<%= canonical %>",
+            "<%= alias %>" => Cow::Borrowed("<%= canonical %>"),
 <% } %>
-            // Known canonical IDs pass through as-is
-            // (leak the string to get &'static str - this is fine since language names are finite)
-            _ => Box::leak(language.to_string().into_boxed_str()),
+            // Unknown language names pass through as-is
+            _ => Cow::Borrowed(language),
         }
     }