docs: comprehensive documentation for HAN-387

- README.md: full project overview, installation, quick start, CLI reference,
  output format descriptions, architecture overview, and dnstraverse comparison
- GoDoc: package-level documentation for traverse, dns, config, output, and
  fingerprint packages
- GoDoc: TraverserConfig and TraversalResult type comments in traverser.go

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: multica-agent <github@multica.ai>

internal/traverse/traverse.go

@@ -1 +1,27 @@
+// Package traverse implements the core DNS traversal engine for ExploreDNS.
+//
+// The traversal engine starts from the DNS root servers and iteratively
+// follows every referral it receives, building a complete picture of the
+// delegation path for a domain.  Unlike a standard recursive resolver, which
+// stops at the first authoritative answer, the traversal engine explores every
+// branch so that delegation mismatches, lame delegations, or split authorities
+// are all visible in the output.
+//
+// # Architecture
+//
+// A Traverser maintains a stack of Referral objects.  Each Referral
+// represents a pending query to a specific set of nameservers for a specific
+// name and record type.  The engine pops referrals one at a time, sends the
+// query, classifies the response, and pushes any child referrals back onto the
+// stack.
+//
+// When a referral contains nameserver names but no glue records (IP addresses),
+// the engine resolves them via a secondary traversal before continuing.
+//
+// # Caching
+//
+// An InfoCache stores discovered glue records.  In fast mode (default) a
+// single root cache is shared across all branches so that glue discovered in
+// one branch is immediately available to sibling branches.  Disable fast mode
+// (TraverserConfig.Fast = false) for fully independent branch resolution.
 package traverse