docs: CLAUDE.md tells the truth about the free suite; make-pdf gate is macOS-only

The '<2s' claim was off by two orders of magnitude (measured 454s serial
at v1.63; ~90-100s now under the parallel runner), and the bare
'bun test' guidance walked the whole repo, loading paid eval files and
missing the strict classifier. Commands now say 'bun run test' with real
numbers, document the strict-output invariant, the EVALS_JOBS /
EVALS_CONCURRENCY split, the computed detach-timeout floor, and the
required free-tests lane. make-pdf-gate drops its Linux leg (redundant
with the free lane running make-pdf tests on every PR); macOS rendering
coverage stays.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/make-pdf-gate.yml

@@ -24,7 +24,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubicloud-standard-8, macos-latest]
+        # macOS only: the Linux leg became redundant when the free-tests lane
+        # started running make-pdf/test (incl. e2e/) on every PR via the
+        # canonical runner — this gate's remaining value is macOS rendering
+        # coverage on make-pdf-scoped changes.
+        os: [macos-latest]
         # Windows is tolerant-mode — Xpdf / Poppler-Windows extraction
         # differs enough from the Linux/macOS baseline that the strict
         # exact-diff gate is unreliable. Enable once the normalized