editors syntax highlighting ...

- emacs syntax: add tree-sitter major mode for SiSU spine markup
  New file sisu-spine-ts-mode.el is a sibling of the existing regex
  mode, backed by Emacs 29+'s built-in treesit.el and the
  tree-sitter-sisu grammar. It replaces the long font-lock keyword list
  with treesit-font-lock-rules grouped into eight features (comment,
  header, heading, block, inline, note, link, index, misc) so users
  can dial verbosity via treesit-font-lock-level. It also wires up:
  - treesit-simple-imenu-settings for a heading outline,
  - treesit-thing-settings for sentence / paragraph motions,
  - treesit-defun-type-regexp so C-M-a / C-M-e jump heading-to-heading,
  - a sisu-spine-ts-install-grammar command that registers
    treesit-language-source-alist and runs
    treesit-install-language-grammar so users can install the parser
    from inside Emacs without leaving the editor.

- the original sisu-spine-mode.el is unchanged and supported for
  Emacs < 29 and for users who prefer regex highlighting.

- nvim drop-in: point parser fetch at tools/tree-sitter-sisu
  sundry/editor-syntax-etc/nvim/
  The nvim-treesitter install_info now fetches the parser from
  https://git.sisudoc.org/projects/tree-sitter-sisu which can be cloned
  via git://git.sisudoc.org/tools/tree-sitter-sisu The fetched paths:
    files = { "src/parser.c", "src/scanner.c" }
  submission of the sisu parser to nvim-treesitter's parsers.lua should
  be a near-trivial one-liner.

- the original vim regex highlighter remains as before
  - sundry/editor-syntax-etc/vim/syntax/sisu-spine.vim
  - sundry/editor-syntax-etc/vim/templates/{sst,ssm,ssi}.tpl
    new skeleton templates for the three SiSU markup file types
    sets up the YAML header (title, creator, date, rights, classify,
    identfier)

- .gitignore - whitelist the new files

(assisted by Claude-Code)

4 files changed, 102 insertions, 2 deletions

diff --git a/sundry/editor-syntax-etc/vim/syntax/sisu-spine.vim b/sundry/editor-syntax-etc/vim/syntax/sisu-spine.vim
index 2de0095..35a893e 100644
--- a/sundry/editor-syntax-etc/vim/syntax/sisu-spine.vim
+++ b/sundry/editor-syntax-etc/vim/syntax/sisu-spine.vim
@@ -1,12 +1,22 @@
-" SiSU Vim syntax    file (sisu-spine)
+" SiSU Vim syntax    file (sisu-spine) - Vim 8 fallback (regex)
 " SiSU Maintainer:   Ralph Amissah <ralph.amissah@gmail.com>
 " SiSU Markup:       SiSU (sisu-5.6.7)
 " sisu-spine Markup: sisu-spine
-" Last Change:       2017-06-22, 2025-02-21
+" Last Change:       2017-06-22, 2025-02-21, 2026-05-09
 " URL: <https://git.sisudoc.org/projects/sisudoc-spine/tree/sundry/editor-syntax-etc/vim/syntax/sisu-spine.vim>
 "      <https://git.sisudoc.org/projects/sisudoc-spine/tree/sundry/editor-syntax-etc/vim/syntax/sisu.vim>
 "      <https://sisudoc.org/>
 "(originally looked at Ruby Vim by Mirko Nasato)
+"
+" Status: This is the regex-based Vim 8 fallback. For Neovim users, the
+" tree-sitter-sisu grammar provides structural highlighting, folding and
+" textobjects with strictly better behaviour on nested markup, multi-line
+" footnotes, block bodies, and segmented headings; see
+"   sundry/editor-syntax-etc/nvim/README.md
+" Emacs 29+ users have an equivalent treesit-based mode at
+"   sundry/editor-syntax-etc/emacs/sisu-spine-ts-mode.el
+" This file remains the supported path for classic Vim, where tree-sitter
+" is not available without third-party plugins.
 
 if version < 600
   syntax clear
diff --git a/sundry/editor-syntax-etc/vim/templates/ssi.tpl b/sundry/editor-syntax-etc/vim/templates/ssi.tpl
new file mode 100644
index 0000000..28e8101
--- /dev/null
+++ b/sundry/editor-syntax-etc/vim/templates/ssi.tpl
@@ -0,0 +1,30 @@
+# SiSU 8.0 insert
+
+title:
+  main:             "#___#"
+  sub:              "#___#"
+  language:         "#___#"
+
+creator:
+  author:           "#___#"
+
+date:
+ :published:        "YYYY-MM-DD"
+
+rights:
+  copyright:        "#___#"
+  license:          "#___#"
+
+classify:
+  topic_register:   "#___#"
+
+make:
+  breaks:           "new=:B; break=1"
+#  home_button_text: "#___#"
+#  footer:           "#___#"
+
+#% -- body ---
+
+:A~ @title @author
+
+1~  #___#
diff --git a/sundry/editor-syntax-etc/vim/templates/ssm.tpl b/sundry/editor-syntax-etc/vim/templates/ssm.tpl
new file mode 100644
index 0000000..579375f
--- /dev/null
+++ b/sundry/editor-syntax-etc/vim/templates/ssm.tpl
@@ -0,0 +1,30 @@
+# SiSU 8.0 master
+
+title:
+  main:             "#___#"
+  sub:              "#___#"
+  language:         "#___#"
+
+creator:
+  author:           "#___#"
+
+date:
+ :published:        "YYYY-MM-DD"
+
+rights:
+  copyright:        "#___#"
+  license:          "#___#"
+
+classify:
+  topic_register:   "#___#"
+
+make:
+  breaks:           "new=:B; break=1"
+#  home_button_text: "#___#"
+#  footer:           "#___#"
+
+#% -- body ---
+
+:A~ @title @author
+
+1~  #___#
diff --git a/sundry/editor-syntax-etc/vim/templates/sst.tpl b/sundry/editor-syntax-etc/vim/templates/sst.tpl
new file mode 100644
index 0000000..069d498
--- /dev/null
+++ b/sundry/editor-syntax-etc/vim/templates/sst.tpl
@@ -0,0 +1,30 @@
+# SiSU 8.0
+
+title:
+  main:             "#___#"
+  sub:              "#___#"
+  language:         "#___#"
+
+creator:
+  author:           "#___#"
+
+date:
+ :published:        "YYYY-MM-DD"
+
+rights:
+  copyright:        "#___#"
+  license:          "#___#"
+
+classify:
+  topic_register:   "#___#"
+
+make:
+  breaks:           "new=:B; break=1"
+#  home_button_text: "#___#"
+#  footer:           "#___#"
+
+#% -- body ---
+
+:A~ @title @author
+
+1~  #___#