feat(init): add LaTeX manual scaffold and 'init manual' command

- scaffolds/manual/: ctexart+xelatex manual template (cover, TOC, colored
  headings, four callout boxes, listings code, booktabs three-line tables),
  visually aligned with Typst md-to-pdf/manual template
- commands/init.py: extract _init_scaffold() shared by paper/manual
- sync README/AGENTS/skill references; document templates-vs-scaffolds-vs-journals taxonomy

README.md

@@ -49,7 +49,7 @@ mytoolkit --help
 | Command | What it does |
 |---------|--------------|
 | `convert` | Universal format conversion (md/img/pdf/eps/avi/bib → pdf/docx/tiff/mp4/md). Auto-detects from extensions. |
-| `init` | Initialize projects/kits from bundled templates (`mytoolkit init paper <dir>`, `mytoolkit init journal <name>`) |
+| `init` | Initialize projects/kits from bundled templates (`mytoolkit init paper|manual <dir>`, `mytoolkit init journal <name>`) |
 | `info` | Show bundled resource paths (`info paths`, `info docs <name>`) |
 | `pdf` | `compress` / `crop` / `merge` / `bookmark` / `to-tiff` |
 | `image` | `compress` / `eps-fix` / `eps-to-pdf` / `jpg-to-pdf` / `tiff-to-pdf` / `tiff-compress` / `generate` (Doubao/Seedream) |
@@ -92,9 +92,11 @@ Registry is stored at `~/.mytoolkit/templates.json` (or `$MYTOOLKIT_HOME/templat
 
 ```bash
 mytoolkit init paper <dir>     # create a LaTeX paper project (Elsevier elsarticle, xelatex, fully portable)
+mytoolkit init manual <dir>    # create a LaTeX manual project (technical/user docs, same style as md-to-pdf/manual)
 ```
 
-This generates `main.tex`, `Makefile`, `references.bib`, `diffpreamble.dtx`, `figs/`.
+`init paper` generates `main.tex`, `Makefile`, `references.bib`, `diffpreamble.dtx`, `figs/`.
+`init manual` generates `main.tex` (cover + TOC + callout boxes + code listing + three-line tables), `Makefile`, `README.md`.
 
 ### Journal submission kits