Repair build and consolidate focused review fixes

A prior fix batch was interrupted mid-change, leaving the tree broken
(JsonLanguage delegated to LanguagePack without the project reference).
This restores a green build and consolidates the coherent fixes:

- JsonLanguage/Grammars.Json now resolve the grammar via LanguagePack
  (chained LanguageNotAvailableException instead of a bare DllNotFound),
  and reference TreeSitter.LanguagePack so the grammar lib ships.
- Parser.Parse throws InvalidOperationException when no language is set;
  null is reserved for timeout/cancellation (test updated to match).
- build-native.ps1 excludes the 3 WASM-only symbols from the synthesized
  .def (they are compiled out of the default no-WASM engine build).
- build-native.sh hard-fails when codesign is unavailable on macOS.
- QueryCursor asserts the should-not-happen capture-array invariant.

Build 0/0; 381 tests pass (incl. a hermetic run with grammar caches removed).

https://claude.ai/code/session_01S3hwvd2oz6cntXmB3G6Yf1

Author: claude

grammars/TreeSitter.Grammars.Json/TreeSitter.Grammars.Json.csproj

@@ -24,13 +24,17 @@
 
   <ItemGroup>
     <ProjectReference Include="..\..\src\TreeSitter\TreeSitter.csproj" />
+    <!-- JsonLanguage resolves the grammar by name via LanguagePack; this reference
+         also makes the json grammar native lib ship transitively (LanguagePack packs
+         the grammar libs under runtimes/<rid>/native/). -->
+    <ProjectReference Include="..\..\src\TreeSitter.LanguagePack\TreeSitter.LanguagePack.csproj" />
   </ItemGroup>
 
   <!--
     Dev/test convenience: copy the JSON grammar native lib next to this assembly so
     the resolver's AssemblyDirectory probe finds libtree-sitter-json.so during
-    `dotnet run`/`dotnet test`. Pack="false": shipping payload travels with the core
-    package's runtimes/<rid>/native assets.
+    `dotnet run`/`dotnet test`. Pack="false": the shipping payload travels with the
+    TreeSitter.LanguagePack package's runtimes/<rid>/native assets (referenced above).
   -->
   <ItemGroup>
     <None Include="$(RepoRoot)native/$(NETCoreSdkPortableRuntimeIdentifier)/libtree-sitter-json.*"

tests/TreeSitter.Tests/ParserTests.cs

@@ -45,11 +45,13 @@ public void TrySetLanguage_null_throws()
     }
 
     [Fact]
-    public void Parse_without_language_returns_null()
+    public void Parse_without_language_throws_InvalidOperation()
     {
         using var parser = new Parser();
-        Assert.Null(parser.Parse("{}"));
-        Assert.Null(parser.Parse("{}"u8));
+        // Parsing with no language set is a programming error (distinct from a
+        // null return, which is reserved for timeout/cancellation).
+        Assert.Throws<InvalidOperationException>(() => parser.Parse("{}"));
+        Assert.Throws<InvalidOperationException>(() => parser.Parse("{}"u8));
     }
 
     [Fact]