internal/pkg: skip resolved cure errors

This significantly improves error resolution performance.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg.go

@@ -947,10 +947,10 @@ func (c *Cache) openFile(f FileArtifact) (r io.ReadCloser, err error) {
 		}
 		if c.msg.IsVerbose() {
 			rn := reportName(f, c.Ident(f))
-			c.msg.Verbosef("curing %s to memory...", rn)
+			c.msg.Verbosef("curing %s in memory...", rn)
 			defer func() {
 				if err == nil {
-					c.msg.Verbosef("cured %s to memory", rn)
+					c.msg.Verbosef("opened %s for reading", rn)
 				}
 			}()
 		}
@@ -1151,6 +1151,9 @@ type DependencyCureError []*CureError
 // unwrapM recursively expands underlying errors into a caller-supplied map.
 func (e *DependencyCureError) unwrapM(me map[unique.Handle[ID]]*CureError) {
 	for _, err := range *e {
+		if _, ok := me[err.Ident]; ok {
+			continue
+		}
 		if _e, ok := err.Err.(*DependencyCureError); ok {
 			_e.unwrapM(me)
 			continue