CK001 used a 300-line file limit as a proxy for single responsibility —
blunt and prone to false positives. CK007 replaces it with LCOM4 (Lack
of Cohesion of Methods), a graph-theoretic metric that proves whether a
struct violates single responsibility by computing connected components
over shared field access. Also fixes the two violations it found:
extracts poll_project_tree to its own file and removes dead worktree
config accessors.

@@ -0,0 +306,4 @@
+// Formatting: human-readable cluster report
+// ---------------------------------------------------------------------------
+
+fn format_clusters(components: &[Vec<String>], info: &ImplInfo) -> String {