docs: add doc.go files and godoc comments to all packages

Add package-level documentation (doc.go) to all 22 first-party
packages and godoc comments to ~150 previously undocumented
exported symbols across common/, network/, and server/.

common/mhfmon/doc.go

@@ -0,0 +1,4 @@
+// Package mhfmon enumerates every monster in Monster Hunter Frontier by its
+// internal enemy ID (em001–em176) and provides metadata such as display name
+// and large/small classification.
+package mhfmon

common/mhfmon/mhfmon.go

@@ -180,11 +180,13 @@ const (
 	KingShakalaka
 )
 
+// Monster holds display metadata for a single monster species.
 type Monster struct {
 	Name  string
 	Large bool
 }
 
+// Monsters is an ordered table of all MHF monsters, indexed by enemy ID.
 var Monsters = []Monster{
 	{"Mon0", false},
 	{"Rathian", true},