docs: comprehensive documentation for ExploreDNS

- Rewrite README.md with overview, features, installation (go install +
  build from source), quick start, full CLI flag reference table,
  output section descriptions, project structure, and development guide

- Add package-level doc comments to all five internal packages:
  config, dns, fingerprint, output, traverse (via doc.go or existing
  package-declaration files)

- Add GoDoc comments on every exported type, constant, function, and
  method across all packages:
  - internal/config: Config struct fields, all Parse*/Default/Validate
  - internal/dns: QueryConfig, Resolver, BasicResolver, CachingResolver,
    ExchangeFunc, RootServer, RootDiscoveryConfig, DecodedResponse,
    ResponseClassification, all exported helpers
  - internal/fingerprint: Fingerprinter, New, NewWithTimeout, Query,
    FingerprintAll
  - internal/traverse: Traverser, TraverserConfig, TraversalResult,
    Referral, ResolutionState, Response, ResponseType, InfoCache,
    Stack, TraverserHooks, EventStage, TraversalEvent, EventHandler,
    CircularReferralError, UnresolvableNameserverError
  - internal/output: Format, Config, Formatter, SummaryStats,
    NewFormatter, AttachHooks, RunTraversal, DefaultConfig,
    ComputeSummary

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

internal/output/runner.go

@@ -9,6 +9,15 @@ import (
 	"github.com/hits/ExploreDNS/internal/traverse"
 )
 
+// RunTraversal is the high-level entry point that wires together a Traverser,
+// a Config, and a Formatter.  It:
+//
+//  1. Attaches output hooks to traverser so events are formatted in real time.
+//  2. Calls traverser.Traverse(ctx, domain) to perform the traversal.
+//  3. Optionally fingerprints encountered servers (when ShowVersions && ShowServers).
+//  4. Writes the summary and flushes the formatter.
+//
+// Returns all TraversalResults and any error from the traversal or output.
 func RunTraversal(ctx context.Context, traverser *traverse.Traverser, cfg *Config, formatter Formatter, domain string) ([]traverse.TraversalResult, error) {
 	if traverser == nil {
 		return nil, fmt.Errorf("traverser is required")