feat(csharp): index C# 12 primary constructors via an up-to-date grammar (#237) (#717)

Vendor tree-sitter-c-sharp 0.23.5 (ABI 15) for C#, replacing the bundled ABI-13
build that dropped primary-constructor classes. Adds native primary-ctor
parsing, primary-ctor parameter dependency edges, return-type extraction via the
renamed `returns` field, and a preParse that blanks `#if` directive lines the
new grammar mis-parses inside enum bodies. Validated on MediatR / eShopOnWeb /
Newtonsoft.Json + full suite.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -51,6 +51,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - C++ free functions are now indexed under their real name. A function written with a qualified-type parameter (`std::string TableFileName(const std::string& dbname)`) or an `auto … -> std::string` trailing return type was mistakenly named after that type (`string`), so calls to it never resolved, `codegraph_node` couldn't find it by name, and the file defining it looked like nothing depended on it. The function now keeps its real name, so cross-file calls, callers, and blast radius work — a meaningful gain for any namespaced C++ codebase (this is how most free functions in a library look). (C++)
 - Ruby impact and `codegraph affected` now follow mixins and `require`s. `include`, `extend`, and `prepend` of a module — Ruby's primary composition mechanism (ActiveSupport concerns, `Comparable`, `Enumerable`) — now record a dependency on that module, so editing a concern surfaces every class that mixes it in; previously these were read as a call to a method named `include`, so a module whose methods are exercised only by application code looked like nothing depended on it. And `require "lib/foo"` / `require_relative "../foo"` now link to the required file, so a file pulled in only by a `require` (config-loaded components, gems that don't autoload) is no longer reported as having no dependents. Together these took a typical gem from ~71% of its files showing real dependents to ~100%. (Ruby)
 - C# `record` types are now indexed. `record`, `record class`, and `record struct` declarations (everywhere in modern C# — DTOs, value objects, CQRS messages, MediatR notifications) were previously skipped entirely, so every reference, generic type argument (`IEnumerable<MyRecord>`), and `new MyRecord(...)` pointed at nothing and the file defining a record looked like it had no callers or dependents. (#237)
+- C# is now parsed with an up-to-date grammar that understands C# 12 **primary constructors**. A class or struct written as `class OrderService(IRepo repo, [FromKeyedServices("primary")] ICache cache) { … }` is now indexed reliably — previously the constructor parameter list confused the parser and could drop the whole class (and all of its methods) from the index, most often exactly when a parameter carried an attribute, as in the ASP.NET keyed-dependency-injection pattern. The primary-constructor parameters are also recorded as dependencies, so the services a type is constructed with show up in its blast radius and "who depends on this contract" answers. Method return types, base types, and members all continue to resolve, and `#if`-guarded members in multi-targeting code keep parsing correctly. (#237)
 - Go interfaces now connect to their implementations. Go has no `implements` keyword — a type satisfies an interface just by having the right methods — so CodeGraph now infers that link: a struct whose methods cover an interface's method set is treated as implementing it, and a call through the interface (`API.Marshal(...)`) reaches every concrete implementation. This means a type used only via an interface (the common plugin/strategy pattern — e.g. JSON-codec or renderer implementations selected at runtime) is no longer reported as having no callers or no dependents, and impact now flows from an interface method to the implementations behind it. (#584)
 - Go now records cross-package struct creation. A composite literal like `render.XML{...}` or `pkga.Widget{...}` — including ones registered in a package-level `var registry = map[string]R{...}` — now links to the package that defines the type. Cross-package function calls and type references already resolved; this closes struct instantiation, so a package whose types are only *constructed* elsewhere (a common pattern for interface implementations) is no longer reported as having no dependents. Go type conversions such as `(*Wrapped)(x)` now link to the converted-to type as well.
 - Python now follows whole-module imports — `from . import certs` then `certs.where()`, or `from pkg import sub` then `sub.run()`. Calls and attribute access through an imported submodule now resolve to that submodule, and importing a module is recorded as a dependency on it even when the member you use is itself re-exported from a third-party package. This also fixed Python relative-import path resolution generally (`from .sub.mod import x`), so `codegraph affected` and impact see the real module graph of a package.