feat: Buchanfang Cover → Titel → Impressum → Inhaltsverzeichnis für alle Bücher

- Kapitelerkennung: erstes Kapitel nur aus einem Bild = Cover ("[Titelinfo]",
  "Deckblatt"), Titel "Titel" = Titelseite
- epub2md_merge: Vorspann reicht bis vor den Hauptteil (Teil, Vorwort,
  Einleitung, nummerierter Titel, > 1000 Wörter), kurze Zwischenseiten
  (Auflage, Verlagsbrief, "Über dieses Buch") bleiben davor
- book.lua: Cover am Inhalt erkannt; LaTeX-Weg (Filter in beiden Schritten):
  \tableofcontents hinter dem Vorspann, \clearpage je Kapitel, kein \maketitle
  vor dem Cover, A4, seitengroßes Cover, DejaVu-Schriften und Mathe-Symbole
  für fehlende Glyphen (Mathebuch: >10.000 fehlende Zeichen → 0)
- Buch-README: bei Formeln LaTeX-Weg empfohlen, sonst weasyprint
- Alle sechs Beispielbücher geprüft: Seite 1 Cover, Verzeichnis nach dem Vorspann

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

pandoc/book.lua

@@ -10,11 +10,13 @@ i.e. before the book's cover, title page and imprint. epub2md_merge.py marks the
 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",
+  * shows the cover (first chapter with nothing but one picture) 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).
+For LaTeX (PDF route md -> html -> pdf, filter in BOTH steps, no --toc) the table of contents becomes
+\tableofcontents at the same place, every chapter starts with \clearpage and there is no \maketitle
+before the cover. 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 \
@@ -73,7 +75,123 @@ local function chapter_anchor(block)
   return id
 end
 
+-- Characters in running text that even DejaVu lacks: typeset as math symbols ("↩︎": footnote back-links).
+local LATEX_SYMBOLS = { ["↩"] = "$\\hookleftarrow$", ["ℓ"] = "$\\ell$", ["\u{2329}"] = "$\\langle$",
+  ["\u{232A}"] = "$\\rangle$", ["\u{3008}"] = "$\\langle$", ["\u{3009}"] = "$\\rangle$",
+  ["∖"] = "$\\setminus$", ["⋯"] = "$\\cdots$", ["\u{FE0E}"] = "" }
+local LATEX_FONTS = { mainfont = "DejaVu Serif", monofont = "DejaVu Sans Mono", mathfont = "DejaVu Math TeX Gyre" }
+
+local function font_installed(name)
+  local pipe = io.popen("fc-list -q " .. string.format("%q", name) .. " && echo yes")
+  local out = pipe and pipe:read("a") or ""
+  if pipe then
+    pipe:close()
+  end
+  return out:match("yes") ~= nil
+end
+
+local function latex_symbols(str)
+  local found = false
+  for _, c in utf8.codes(str.text) do
+    if LATEX_SYMBOLS[utf8.char(c)] then
+      found = true
+      break
+    end
+  end
+  if not found then
+    return nil
+  end
+  local out, buf = pandoc.Inlines({}), {}
+  for _, c in utf8.codes(str.text) do
+    local ch = utf8.char(c)
+    local tex = LATEX_SYMBOLS[ch]
+    if tex then
+      if #buf > 0 then
+        out:insert(pandoc.Str(table.concat(buf)))
+        buf = {}
+      end
+      if tex ~= "" then
+        out:insert(pandoc.RawInline("latex", tex))
+      end
+    else
+      buf[#buf + 1] = ch
+    end
+  end
+  if #buf > 0 then
+    out:insert(pandoc.Str(table.concat(buf)))
+  end
+  return out
+end
+
+-- LaTeX (2nd step of the PDF route md -> html -> pdf): the HTML from step 1 already holds the table of
+-- contents (div#TOC.toc), the chapter starts (div.chapter-start) and, if moved, Pandoc's title block.
+local function latex_book(doc)
+  local found = false
+  doc.blocks:walk({ Div = function(d)
+    if d.identifier == "TOC" and d.classes:includes("toc") or d.classes:includes("chapter-start") then
+      found = true
+    end
+  end })
+  if not found then
+    return nil
+  end
+  local blocks = pandoc.Blocks({})
+  for _, block in ipairs(doc.blocks) do
+    if block.t == "Div" and block.identifier == "TOC" and block.classes:includes("toc") then
+      blocks:insert(pandoc.RawBlock("latex", "\\clearpage\n\\tableofcontents\n\\clearpage"))
+    elseif block.t == "Div" and block.classes:includes("chapter-start") then
+      blocks:insert(pandoc.RawBlock("latex", "\\clearpage"))
+      blocks:insert(block)
+    elseif block.t == "Div" and block.classes:includes("cover") then
+      blocks:insert(block:walk({ Image = function(img) -- cover as large as the page allows
+        img.attributes.width = nil
+        img.attributes.height = "20cm"
+        return img
+      end }))
+    elseif block.t == "Div" and block.identifier == "title-block-header" then
+      blocks:insert(pandoc.RawBlock("latex", "\\clearpage\n\\begin{center}\n\\vspace*{3cm}"))
+      for _, b in ipairs(block.content) do
+        if b.t == "Header" then
+          local title = pandoc.Inlines({ pandoc.RawInline("latex", "{\\Huge\\bfseries ") })
+          title:extend(b.content)
+          title:insert(pandoc.RawInline("latex", "}"))
+          blocks:insert(pandoc.Para(title))
+        else
+          blocks:insert(b)
+        end
+      end
+      blocks:insert(pandoc.RawBlock("latex", "\\end{center}"))
+    else
+      blocks:insert(block)
+    end
+  end
+  doc.blocks = blocks:walk({ Str = latex_symbols })
+  -- fonts with a wide Unicode coverage (∈ λ ≠ ≥ □, thin spaces …), unless the user chose fonts himself
+  -- A4 with moderate margins, like print.css (Pandoc's LaTeX default: US letter, wide margins)
+  doc.meta.papersize = doc.meta.papersize or "a4"
+  doc.meta.geometry = doc.meta.geometry or "margin=2cm"
+  for var, font in pairs(LATEX_FONTS) do
+    if doc.meta[var] == nil and font_installed(font) then
+      doc.meta[var] = font
+    end
+  end
+  -- no \maketitle at the very top (before the cover); keep the PDF metadata
+  if doc.meta.title then
+    doc.meta["title-meta"] = pandoc.utils.stringify(doc.meta.title)
+    doc.meta.title = nil
+  end
+  if doc.meta.author then
+    doc.meta["author-meta"] = pandoc.utils.stringify(doc.meta.author)
+    doc.meta.author = nil
+  end
+  doc.meta.date = nil
+  return doc
+end
+
 function Pandoc(doc)
+  if FORMAT:match("latex") then
+    return latex_book(doc)
+  end
   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
@@ -98,6 +216,7 @@ function Pandoc(doc)
   end
 
   local blocks = pandoc.Blocks({})
+  local seen_chapter = false
   for i, block in ipairs(doc.blocks) do
     local anchor = chapter_anchor(block)
     if i == toc_at then
@@ -117,15 +236,26 @@ function Pandoc(doc)
       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 = {}
+      -- cover: the first chapter, if it holds nothing but one picture ('Cover', '[Titelinfo]', 'Deckblatt' …);
+      -- shown without the caption "Cover", centred on its own page
+      local nxt, after = doc.blocks[i + 1], doc.blocks[i + 2]
+      local ends = after == nil or chapter_anchor(after) ~= nil or is_placeholder(after, TOC_ID)
+        or is_placeholder(after, TITLE_ID)
+      if not seen_chapter and nxt and (nxt.t == "Figure" or nxt.t == "Para") and ends then
+        local imgs, text = {}, false
         nxt:walk({ Image = function(img) imgs[#imgs + 1] = img end })
-        if #imgs == 1 then
+        if nxt.t == "Para" then
+          for _, inl in ipairs(nxt.content) do
+            if inl.t ~= "Image" and inl.t ~= "Space" and inl.t ~= "SoftBreak" then
+              text = true
+            end
+          end
+        end
+        if #imgs == 1 and not text then
           doc.blocks[i + 1] = pandoc.Div({ pandoc.Plain({ imgs[1] }) }, pandoc.Attr("", { "cover" }))
         end
       end
+      seen_chapter = true
     else
       blocks:insert(block)
     end