feat(expo-router): add Expo Router support for screens and navigates

Introduce Expo Router integration: a new framework resolver, route-based screen nodes, and navigates edges, plus a /api/screens endpoint and a Screens UI view. Adds branch-guard-driven labeling of edges, resolution logic, and tests to cover extraction, resolution, and end-to-end flow. This enables CodeGraph UI to surface screens and transitions from Expo Router apps.

codegraph-kernel/src/buffers.rs

@@ -104,7 +104,7 @@ pub const NODE_KINDS: [&str; 23] = [
 ];
 
 /// Mirror of EDGE_KINDS in src/types.ts — order is the wire contract.
-pub const EDGE_KINDS: [&str; 12] = [
+pub const EDGE_KINDS: [&str; 13] = [
     "contains",
     "calls",
     "imports",
@@ -117,6 +117,7 @@ pub const EDGE_KINDS: [&str; 12] = [
     "instantiates",
     "overrides",
     "decorates",
+    "navigates",
 ];
 
 /// ReferenceKind code for the internal-only `function_ref` (#756).