feat: Inhaltsverzeichnis nach Cover, Titelseite und Impressum (pandoc/book.lua)

Pandocs --toc setzt Inhaltsverzeichnis und Titelkopf immer vor den
Buchtext, also vor Cover, Titelseite und Impressum.

- epub2md_merge.py: Kapiteltypen aus manifest.json; Platzhalter
  <div id="epub2md-toc"> hinter dem Vorspann und, ohne eigene Titelseite,
  <div id="epub2md-titlepage"> hinter dem Cover; --toc-Liste an derselben Stelle
- pandoc/book.lua (HTML/weasyprint, statt --toc): baut dort das
  Inhaltsverzeichnis, lässt Pandocs Titelkopf bei eigener Titelseite weg,
  Cover ohne Bildunterschrift, Kapitelanker → div.chapter-start;
  andere Formate: nur Platzhalter entfernen
- print.css: jedes Kapitel (auch Cover/Titelseite/Impressum) und das
  Verzeichnis auf neuer Seite, Verzeichnis mit Punktlinie und Seitenzahl
- Buch-README, Bedienungsanleitung, README: Befehle mit book.lua

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

pandoc/book.lua

@@ -0,0 +1,140 @@
+--[[
+book.lua – Pandoc filter for book files from epub2md_merge.py (HTML output, e.g. PDF via weasyprint).
+
+Pandoc's --toc always puts the table of contents (and its own title block) before the whole text,
+i.e. before the book's cover, title page and imprint. epub2md_merge.py marks the right places:
+
+    <div id="epub2md-titlepage"></div>   after the cover, only if the book has no title page of its own
+    <div id="epub2md-toc"></div>         after the front matter (cover, title page, imprint …)
+
+This filter, for HTML output:
+  * builds the table of contents at the placeholder (use it INSTEAD of --toc; --toc-depth is honoured),
+  * drops Pandoc's title block when the book has its own title page, or moves it to the placeholder,
+  * shows the cover picture (chapter "NNN-cover") without the caption "Cover",
+  * turns the chapter anchors <a id="001-…"></a> into <div class="chapter-start"> so that print.css can
+    start every chapter – including cover, title page and imprint – on a new page.
+
+For other formats it only removes the placeholders (EPUB, DOCX, ODT: use --toc there).
+
+Usage:
+    pandoc buch.md -s --lua-filter /pfad/zu/epub2md/pandoc/book.lua \
+      --lua-filter /pfad/zu/epub2md/pandoc/callouts.lua --css /pfad/zu/epub2md/pandoc/print.css \
+      --pdf-engine=weasyprint -o buch.pdf
+]]
+
+local TOC_ID, TITLE_ID = "epub2md-toc", "epub2md-titlepage"
+local TOC_TITLE = { de = "Inhaltsverzeichnis", en = "Contents" }
+
+local function is_placeholder(block, id)
+  return block.t == "Div" and block.identifier == id and #block.content == 0
+end
+
+local function esc(s)
+  return (s:gsub("&", "&amp;"):gsub("<", "&lt;"):gsub(">", "&gt;"))
+end
+
+-- <header id="title-block-header"> as Pandoc's HTML template writes it.
+local function title_block(meta)
+  local html = { '<header id="title-block-header">', '<h1 class="title">' .. esc(pandoc.utils.stringify(meta.title)) .. "</h1>" }
+  if meta.subtitle then
+    html[#html + 1] = '<p class="subtitle">' .. esc(pandoc.utils.stringify(meta.subtitle)) .. "</p>"
+  end
+  local authors = meta.author
+  if authors and pandoc.utils.type(authors) ~= "List" then
+    authors = { authors }
+  end
+  for _, a in ipairs(authors or {}) do
+    html[#html + 1] = '<p class="author">' .. esc(pandoc.utils.stringify(a)) .. "</p>"
+  end
+  if meta.date then
+    html[#html + 1] = '<p class="date">' .. esc(pandoc.utils.stringify(meta.date)) .. "</p>"
+  end
+  html[#html + 1] = "</header>"
+  return pandoc.RawBlock("html", table.concat(html, "\n"))
+end
+
+-- Paragraph that only holds chapter start anchors (<a id="001-cover"></a>) → id of the first one.
+local function chapter_anchor(block)
+  if block.t ~= "Para" and block.t ~= "Plain" then
+    return nil
+  end
+  local id = nil
+  for _, inl in ipairs(block.content) do
+    if inl.t ~= "RawInline" then
+      return nil
+    end
+    local found = inl.text:match('^<a id="(%d%d%d%-[^"]*)">$') or inl.text:match('^<a id="(%d%d%d%-[^"]*)"></a>$')
+    if found then
+      id = id or found
+    elseif inl.text ~= "</a>" then
+      return nil
+    end
+  end
+  return id
+end
+
+function Pandoc(doc)
+  local html = FORMAT:match("html") and not FORMAT:match("epub")
+  local toc_at, title_at = nil, nil
+  for i, block in ipairs(doc.blocks) do
+    if is_placeholder(block, TOC_ID) then
+      toc_at = i
+    elseif is_placeholder(block, TITLE_ID) then
+      title_at = i
+    end
+  end
+  if not toc_at and not title_at then
+    return nil -- not a file from epub2md_merge.py
+  end
+  if not html then -- placeholders are top-level blocks: just drop them
+    local kept = pandoc.Blocks({})
+    for _, block in ipairs(doc.blocks) do
+      if not is_placeholder(block, TOC_ID) and not is_placeholder(block, TITLE_ID) then
+        kept:insert(block)
+      end
+    end
+    doc.blocks = kept
+    return doc
+  end
+
+  local blocks = pandoc.Blocks({})
+  for i, block in ipairs(doc.blocks) do
+    local anchor = chapter_anchor(block)
+    if i == toc_at then
+      if PANDOC_WRITER_OPTIONS.table_of_contents then
+        -- --toc given as well: Pandoc's own table of contents stays at the top, no second one
+      else
+        local lang = doc.meta.lang and pandoc.utils.stringify(doc.meta.lang):sub(1, 2):lower() or "de"
+        local toc = pandoc.structure.table_of_contents(doc.blocks, PANDOC_WRITER_OPTIONS)
+        blocks:insert(pandoc.Div({
+          pandoc.Header(1, TOC_TITLE[lang] or TOC_TITLE.de, pandoc.Attr("toc-title", { "unnumbered", "unlisted" })),
+          toc,
+        }, pandoc.Attr("TOC", { "toc" })))
+      end
+    elseif i == title_at then
+      if doc.meta.title then
+        blocks:insert(title_block(doc.meta))
+      end
+    elseif anchor then
+      blocks:insert(pandoc.Div({}, pandoc.Attr(anchor, { "chapter-start" })))
+      local nxt = doc.blocks[i + 1]
+      if anchor:match("^%d%d%d%-cover") and nxt and nxt.t == "Figure" then
+        -- cover chapter: the picture without the caption "Cover", centred on its own page
+        local imgs = {}
+        nxt:walk({ Image = function(img) imgs[#imgs + 1] = img end })
+        if #imgs == 1 then
+          doc.blocks[i + 1] = pandoc.Div({ pandoc.Plain({ imgs[1] }) }, pandoc.Attr("", { "cover" }))
+        end
+      end
+    else
+      blocks:insert(block)
+    end
+  end
+  doc.blocks = blocks
+  -- The book's own title page (or the moved block) replaces Pandoc's title block at the very top.
+  if doc.meta.title then
+    doc.meta.pagetitle = doc.meta.pagetitle or pandoc.utils.stringify(doc.meta.title)
+    doc.meta.title = nil
+  end
+  return doc
+end