make-pdf: --toc page-number cells are always empty (no target-counter rule in the print CSS) #2903

Summary

make-pdf --toc renders a table of contents with title text and dotted leaders, but
every page-number cell is empty. The leaders run into blank space. The skill
documents this flag as "Clickable TOC with page numbers", so the page-number half is
missing.

This is not #1689. That issue's root cause (TOC anchors pointing at ids no heading
carried) is fixed — see verification below. The anchors resolve now; the page numbers
still never appear, for a different reason.

Environment

• gstack 1.87.4.0 (global install, ./setup --prefix)
• macOS (arm64), printed through Aside 1.26.916.1741
• 6-page document, --cover --toc, 7 headings

Verification that #1689 is fixed

Generated with --to html and inspected:

TOC anchor hrefs:      ['toc-0' ... 'toc-6']  (total 7)
heading ids in body:   ['toc-0' ... 'toc-6']  (total 7)
anchors that RESOLVE:   7 / 7
data-toc-target ids:    7, targets that RESOLVE: 7 / 7

Every anchor and every data-toc-target now resolves to a real heading id. #1990 did
its job.

The remaining bug

The same HTML shows:

toc-page spans:         7
  non-empty:            0
  sample raw:           ''
target-counter( usage:  NONE

buildTocBlock emits <span class="toc-page" data-toc-target="toc-N"></span> empty,
with the comment that "Page numbers are filled in by Paged.js". But nothing in the
print CSS ever asks Paged.js to fill them. There is no target-counter() declaration
anywhere in the generated stylesheet, so the spans stay empty through the entire print
run.

For completeness, the one rule that hides them:

.toc li .toc-page, .toc li .toc-dots { display: none; }

is inside @media screen and is correct — screen HTML has no pages. It is not the
cause; the print path simply has nothing to render.

Reproduce

printf '# One\n\nbody\n\n# Two\n\nbody\n' > /tmp/t.md
$P generate --toc /tmp/t.md /tmp/t.pdf
pdftotext -f 2 -l 2 /tmp/t.pdf -   # TOC page: titles present, no page numbers

Or inspect the HTML directly:

$P generate --toc /tmp/t.md /tmp/t.html --to html
grep -o 'target-counter([^)]*)' /tmp/t.html   # no output

Expected

Each .toc-page span resolves to the printed page number of its target heading, e.g.
via a Paged.js target-counter rule in the print stylesheet:

.toc-page::after { content: target-counter(attr(data-toc-target), page); }

(exact form depending on how the target id is threaded through).

Suggested follow-up

#1689 can probably be closed — its stated root cause is resolved, and a commenter has
already asked for that. This ticket covers the symptom that outlived the fix.