P5a review: outlines from named destinations; pool race; fast over-limit; revalidation under the limiter; Accept pdf

- pdftext/outline: resolve named destinations through the catalog /Dests and the /Names /Dests
  tree, resolve indirect /Dest, /A and /Title, and treat reader.Null (what Dict.Get returns for
  a missing key) as absent. Before this every LaTeX and Acrobat PDF had an empty outline.
  pdftest gains NamedDests; TestOutlineNamedDestinations.
- api: pool() always goes through its Once (data race on concurrent first use);
  TestDefaultPoolConcurrentFirstUse. Revalidation of a stale cache entry counts against the
  caller/host limit.
- pdftext/runner: output over MaxText kills the child at once instead of waiting for the
  deadline; TestRunnerTooMuchTextFailsFast.
- fetch: Accept includes application/pdf;q=0.8.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/pdftext/pdftext.go

@@ -148,7 +148,7 @@ func infoTitle(doc *reader.Document) string {
 	if !ok {
 		return ""
 	}
-	return textString(d.Get("Title"))
+	return textString(resolve(doc, d.Get("Title"))) // the title may be an indirect object
 }
 
 // textString decodes a reader.String (raw bytes) as a PDF text string per rule 3.