epub, html: document heads and ids, fixes

One document head per file, and ids must be unique. No remaining fatal
errors in the epub in the marup sample set.

(assisted by Claude-Code)

3 files changed, 26 insertions, 12 deletions

diff --git a/org/out_xmls.org b/org/out_xmls.org
index dac590e..5b989df 100644
--- a/org/out_xmls.org
+++ b/org/out_xmls.org
@@ -639,7 +639,7 @@ string tail(M)(M doc_matters) {
   string o;
   o = format(q"┃<hr />
   <div class="rights">
-    <p class="small" id="copyright"><a name="copyright"></a>
+    <p class="small" id="copyright">
       <b>Copyright:</b> %s
     </p>
   </div>
@@ -651,10 +651,10 @@ string tail(M)(M doc_matters) {
   </div>
   <hr />
   <div class="generator">
-    <p class="small_center" id="sisu_spine"><a name="sisu_spine"></a>
+    <p class="small_center" id="sisu_spine">
       <a href="https://sisudoc.org" class="lnkicon">≅ SiSU Spine ፨</a> (object numbering &amp; object search)
     </p>
-    <p class="small_center" id="sisu_spine"><a name="sisu_spine"></a>
+    <p class="small_center" id="sisu_spine_dates">
       (web 1993, object numbering 1997, object search 2002 ...) <<year>>
     </p>
   </div>
@@ -1107,7 +1107,7 @@ string heading(O,M)(
     if (obj.metainfo.is_of_section == "toc") {
       o ~= format(q"┃
   <div class="substance">
-    <p class="small" id="copyright"><a name="copyright"></a>
+    <p class="small" id="copyright_toc">
       Copyright: %s
     </p>
     <!-- <p class="small" id="rights"><a name="rights"></a>
@@ -2815,6 +2815,13 @@ string epub3_oebps_toc_nav_xhtml(D)(D doc) {
   static auto rgx = RgxO();
   static auto rgx_xhtml = RgxXHTML();
   string segment_filename;
+  /+ ↓ a segment file gets one document head, not one per heading. +/
+  bool[string] _seg_head_written;
+  string _segHead(M)(M _m, string _seg) {
+    if (_seg in _seg_head_written) { return ""; }
+    _seg_head_written[_seg] = true;
+    return xhtml_format.epub3_seg_head(_m);
+  }
   string[] top_level_headings = ["","","",""];
   string[string] oepbs_content_parts;
   bool[string]   _segment_files_seen;   /+ a segment file is listed once +/
@@ -2872,7 +2879,7 @@ if (obj.metainfo.is_a == "heading") {
       goto default;
     default:
       epubWrite.doc_parts ~= obj.tags.segment_anchor_tag_epub;
-      epubWrite.doc_epub3[obj.tags.segment_anchor_tag_epub] ~= xhtml_format.epub3_seg_head(doc.matters);
+      epubWrite.doc_epub3[obj.tags.segment_anchor_tag_epub] ~= _segHead(doc.matters, obj.tags.segment_anchor_tag_epub);
       Tuple!(string, string[]) t = xhtml_format.heading_seg(_txt, obj, doc.matters, suffix, "epub");
       epubWrite.doc_epub3[obj.tags.segment_anchor_tag_epub] ~= t[0];
       epubWrite.doc_epub3_endnotes[obj.tags.segment_anchor_tag_epub] ~= t[1];
@@ -2881,7 +2888,7 @@ if (obj.metainfo.is_a == "heading") {
     break;
   case 4:
     segment_filename = obj.tags.segment_anchor_tag_epub;
-    epubWrite.doc_epub3[segment_filename] ~= xhtml_format.epub3_seg_head(doc.matters);
+    epubWrite.doc_epub3[segment_filename] ~= _segHead(doc.matters, segment_filename);
     Tuple!(string, string[]) t = xhtml_format.heading_seg(_txt, obj, doc.matters, suffix, "epub");
     epubWrite.doc_epub3[segment_filename] ~= t[0];
     epubWrite.doc_epub3_endnotes[segment_filename] ~= t[1];
diff --git a/src/sisudoc/outputs/io_out/epub3.d b/src/sisudoc/outputs/io_out/epub3.d
index d149dac..1c08bab 100644
--- a/src/sisudoc/outputs/io_out/epub3.d
+++ b/src/sisudoc/outputs/io_out/epub3.d
@@ -306,6 +306,13 @@ template outputEPub3() {
     static auto rgx = RgxO();
     static auto rgx_xhtml = RgxXHTML();
     string segment_filename;
+    /+ ↓ a segment file gets one document head, not one per heading. +/
+    bool[string] _seg_head_written;
+    string _segHead(M)(M _m, string _seg) {
+      if (_seg in _seg_head_written) { return ""; }
+      _seg_head_written[_seg] = true;
+      return xhtml_format.epub3_seg_head(_m);
+    }
     string[] top_level_headings = ["","","",""];
     string[string] oepbs_content_parts;
     bool[string]   _segment_files_seen;   /+ a segment file is listed once +/
@@ -351,7 +358,7 @@ template outputEPub3() {
               goto default;
             default:
               epubWrite.doc_parts ~= obj.tags.segment_anchor_tag_epub;
-              epubWrite.doc_epub3[obj.tags.segment_anchor_tag_epub] ~= xhtml_format.epub3_seg_head(doc.matters);
+              epubWrite.doc_epub3[obj.tags.segment_anchor_tag_epub] ~= _segHead(doc.matters, obj.tags.segment_anchor_tag_epub);
               Tuple!(string, string[]) t = xhtml_format.heading_seg(_txt, obj, doc.matters, suffix, "epub");
               epubWrite.doc_epub3[obj.tags.segment_anchor_tag_epub] ~= t[0];
               epubWrite.doc_epub3_endnotes[obj.tags.segment_anchor_tag_epub] ~= t[1];
@@ -360,7 +367,7 @@ template outputEPub3() {
             break;
           case 4:
             segment_filename = obj.tags.segment_anchor_tag_epub;
-            epubWrite.doc_epub3[segment_filename] ~= xhtml_format.epub3_seg_head(doc.matters);
+            epubWrite.doc_epub3[segment_filename] ~= _segHead(doc.matters, segment_filename);
             Tuple!(string, string[]) t = xhtml_format.heading_seg(_txt, obj, doc.matters, suffix, "epub");
             epubWrite.doc_epub3[segment_filename] ~= t[0];
             epubWrite.doc_epub3_endnotes[segment_filename] ~= t[1];
diff --git a/src/sisudoc/outputs/io_out/xmls.d b/src/sisudoc/outputs/io_out/xmls.d
index 3f7f4c9..f1bcd95 100644
--- a/src/sisudoc/outputs/io_out/xmls.d
+++ b/src/sisudoc/outputs/io_out/xmls.d
@@ -495,7 +495,7 @@ string tail(M)(M doc_matters) {
   string o;
   o = format(q"┃<hr />
   <div class="rights">
-    <p class="small" id="copyright"><a name="copyright"></a>
+    <p class="small" id="copyright">
       <b>Copyright:</b> %s
     </p>
   </div>
@@ -507,10 +507,10 @@ string tail(M)(M doc_matters) {
   </div>
   <hr />
   <div class="generator">
-    <p class="small_center" id="sisu_spine"><a name="sisu_spine"></a>
+    <p class="small_center" id="sisu_spine">
       <a href="https://sisudoc.org" class="lnkicon">≅ SiSU Spine ፨</a> (object numbering &amp; object search)
     </p>
-    <p class="small_center" id="sisu_spine"><a name="sisu_spine"></a>
+    <p class="small_center" id="sisu_spine_dates">
       (web 1993, object numbering 1997, object search 2002 ...) 2026
     </p>
   </div>
@@ -903,7 +903,7 @@ string tail(M)(M doc_matters) {
         if (obj.metainfo.is_of_section == "toc") {
           o ~= format(q"┃
       <div class="substance">
-        <p class="small" id="copyright"><a name="copyright"></a>
+        <p class="small" id="copyright_toc">
           Copyright: %s
         </p>
         <!-- <p class="small" id="rights"><a name="rights"></a>