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/api/pdf_review_test.go

@@ -0,0 +1,30 @@
+package api
+
+// Owner review (P5a): the default pool is built once, safely, when concurrent first requests
+// arrive on a server with no pool configured (run under -race).
+
+import (
+	"sync"
+	"testing"
+)
+
+func TestDefaultPoolConcurrentFirstUse(t *testing.T) {
+	s, _ := setupAPI(t, nil)
+	var wg sync.WaitGroup
+	got := make(chan any, 16)
+	for i := 0; i < 16; i++ {
+		wg.Add(1)
+		go func() { defer wg.Done(); got <- s.pool() }()
+	}
+	wg.Wait()
+	close(got)
+	var first any
+	for p := range got {
+		if first == nil {
+			first = p
+		}
+		if p != first || p == nil {
+			t.Fatal("pool() returned different or nil pools")
+		}
+	}
+}