[ANE-512] Fix Cargo analyzer reporting library as dependency of itself

The Cargo analyzer was incorrectly reporting library projects as dependencies
of themselves when they had no external dependencies. This occurred because
the buildGraph function treated all workspace members as direct dependencies
without filtering out isolated workspace members from the final graph.

The fix uses Graphing.shrink to filter out workspace members that have no
external dependencies, while preserving workspace members that do have
legitimate external dependencies. This maintains backward compatibility
with existing workspace projects while fixing the self-dependency issue
for isolated library projects.

Fixes ISS-679

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: ryanlink

src/Strategy/Cargo.hs

@@ -46,7 +46,9 @@ import Data.Functor (void)
 import Data.List.NonEmpty qualified as NonEmpty
 import Data.Map.Strict qualified as Map
 import Data.Maybe (catMaybes, fromMaybe, isJust)
+import Data.List (find)
 import Data.Set (Set)
+import Data.Set qualified as Set
 import Data.String.Conversion (toString, toText)
 import Data.Text (Text)
 import Data.Text qualified as Text
@@ -76,7 +78,7 @@ import Effect.Grapher (
 import Effect.ReadFS (ReadFS, doesFileExist, readContentsToml)
 import Errata (Errata (..))
 import GHC.Generics (Generic)
-import Graphing (Graphing, stripRoot)
+import Graphing (Graphing, shrink, stripRoot)
 import Path (Abs, Dir, File, Path, mkRelFile, parent, parseRelFile, toFilePath, (</>))
 import Text.Megaparsec (
   Parsec,
@@ -406,10 +408,29 @@ addEdge node = do
     edge parentId $ nodePkg dep
 
 buildGraph :: CargoMetadata -> Graphing Dependency
-buildGraph meta = stripRoot $
+buildGraph meta = stripRoot . shrink isNotWorkspaceMember $
   run . withLabeling toDependency $ do
     traverse_ direct $ metadataWorkspaceMembers meta
     traverse_ addEdge $ resolvedNodes $ metadataResolve meta
+  where
+    -- Create a set of workspace members that have no external dependencies
+    isolatedWorkspaceMembers = Set.fromList $ map packageKey $ filter hasNoDependencies $ metadataWorkspaceMembers meta
+    packageKey :: PackageId -> (Text, Text)
+    packageKey pkg = (pkgIdName pkg, pkgIdVersion pkg)
+    
+    -- Check if a workspace member has no dependencies by looking at resolve nodes
+    hasNoDependencies :: PackageId -> Bool
+    hasNoDependencies pkgId = 
+      case find (\node -> resolveNodeId node == pkgId) (resolvedNodes $ metadataResolve meta) of
+        Just node -> null (resolveNodeDeps node)
+        Nothing -> True -- If not found in resolve, assume no dependencies
+
+    -- Filter out isolated workspace members only
+    isNotWorkspaceMember :: Dependency -> Bool
+    isNotWorkspaceMember dep =
+      case dependencyVersion dep of
+        Just (CEq version) -> (dependencyName dep, version) `Set.notMember` isolatedWorkspaceMembers
+        _ -> True
 
 -- | Custom Parsec type alias
 type PkgSpecParser a = Parsec Void Text a