docs: add package docs to trace and verifier

internal/trace/writer.go

@@ -1,3 +1,4 @@
+// Package trace records each run's steps, snapshots, and violations to disk for later inspection.
 package trace
 
 import (

internal/verifier/worker.go

@@ -1,3 +1,4 @@
+// Package verifier runs the spec's extractors and property formulas against each observed step.
 package verifier
 
 import (