docs(agents): fix runtime version, blob reader name, and bridge utility references

- Runtime: macOS 10.15 → 11.0 (matches actual deployment target)
- KeyValueBlobReader → MemoryMappedFile (correct utility name)
- NSStringUtils → Foundation methods (NSStringUtils is Swift-only)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: tianjianjiang

AGENTS.md

@@ -40,7 +40,7 @@ McBopomofo (小麥注音輸入法) is a Traditional Chinese input method engine
 
 ## System Requirements
 
-**Runtime:** macOS 10.15 (Catalina) or later
+**Runtime:** macOS 11.0 (Big Sur) or later
 
 **Development:**
 - macOS 14.7 or later
@@ -247,7 +247,7 @@ McBopomofo uses a three-layer architecture (Swift/Objective-C++/C++). For detail
 - Manage C++ object lifetimes in `.mm` files with proper `init`/`dealloc`
 - Use `std::shared_ptr` when passing to C++ APIs
 - Surface engine capabilities by extending bridge classes and declaring in `McBopomofo-Bridging-Header.h`
-- Convert between `NSString` and `std::string` using `UTF8Helper`/`NSStringUtils`, not manual conversion
+- Convert between `NSString` and `std::string` using `UTF8Helper` and Foundation methods, not manual conversion
 - Keep bridge methods small: forward to engine, return Foundation types
 
 </required>
@@ -265,7 +265,7 @@ McBopomofo uses a three-layer architecture (Swift/Objective-C++/C++). For detail
   `std::string_view`
 - Place code in existing namespaces: `McBopomofo`,
   `Formosa::Gramambular2`, `Formosa::Mandarin`
-- Reuse blob readers (`KeyValueBlobReader`,
+- Reuse blob readers (`MemoryMappedFile`,
   `ParselessPhraseDB`, `PhraseReplacementMap`)
 - Keep algorithms deterministic and side-effect free;
   logging stays in Objective-C++ layer