feat(protobuf): gRPC service/rpc + make proto message/schema reach the graph

crates/ecp-analyzer/src/protobuf/mod.rs

@@ -1,4 +1,5 @@
-//! Protobuf `.proto` file analysis — T4-5 schema-field detector.
+//! Protobuf `.proto` file analysis — message structs, schema fields, and
+//! gRPC service contracts.
 //!
 //! Uses a hand-rolled line-oriented lexer (Option B) because no
 //! `tree-sitter-protobuf` crate exists in the workspace.  The lexer handles
@@ -11,12 +12,20 @@
 //! }
 //! ```
 //!
+//! Each top-level `message` with ≥1 field becomes a `NodeKind::Struct`
+//! (value-type aggregate — no inheritance/vtable, distinct from `Class`),
+//! owning its fields via `HasProperty`. Without this owner node the schema
+//! fields are dropped at `schema_field_mirrors` and never reach the graph.
+//!
 //! **Acknowledged limitations (v1)**:
 //! - Nested `message` definitions are skipped (parser does not recurse).
 //! - `oneof` blocks are not supported — fields inside them are not emitted.
 //! - `map<K,V>` fields are not supported — skipped with no emission.
 //! - `enum` definitions are ignored (no `SchemaField` equivalent).
-//! - RPC / service blocks are ignored.
+//! - `service { rpc … }` blocks ARE captured: each `rpc` becomes a
+//!   `NodeKind::Route` (method `GRPC`, path `/<package.>Service/Method`) so
+//!   gRPC service contracts are visible to `ecp routes` / `ecp contracts`.
+//!   Nested services and rpc request/response message types are not captured.
 //! - Multi-line comments (`/* … */`) are treated as opaque — a field
 //!   declaration whose line falls inside a block comment may be emitted.
 //!   Single-line `//` comments are stripped correctly.