Add per-category line-height support

Nastaliq and other complex scripts need significantly more vertical
space than Latin text. A new `line-height` key on any category entry
in config.yml overrides --line-height-body for that category and
restores the theme default when switching away.

https://claude.ai/code/session_01LZVnq4wUgdv5oXFLcj6qXf

CLAUDE.md

@@ -166,6 +166,7 @@ For nested navigation, set `parent: <parent-section-code>` and `parent-sort` on
 - Variant files: `<base>.<code>.md` — the suffix is only treated as a category if the code is declared in config
 - `categories-sectionnames: per-category` requires each section in `nav.yml` to have a `categorynames` block with an entry per category code
 - RTL is set per category via `direction: rtl`
+- Line height is set per category via `line-height: 2.8` (useful for scripts like Nastaliq that need extra vertical space). Restores to theme default when switching to a category without this key.
 
 ## Dynamic post tags (mdcms code blocks)
 

app/index.html

@@ -957,6 +957,7 @@ body {
   let activeCategory = null;      // current code
   let sectionnamesMode = 'same';  // 'same' | 'per-category'
   let loadedFonts = new Set();    // track which font files have been loaded
+  let defaultLineHeight = null;   // theme/CSS default, captured after theme is applied
 
   // ─── Icons ────────────────────────────────────────────────
   const STANDARD_ICONS = ['dark_mode','light_mode','menu','search','arrow_right','arrow_drop_down','mobile_arrow_down','language','info','warning','error','success','exclamation','dangerous','report','history','text_compare','keyboard_arrow_right','keyboard_arrow_down','keyboard_double_arrow_right','keyboard_double_arrow_down','expand_content','collapse_content','add','minimize'];
@@ -2298,6 +2299,9 @@ function fmtDatetime(dtStr) {
     document.querySelectorAll('.category-bar').forEach(b => b.setAttribute('dir', direction));
     document.querySelectorAll('.md-content, .title-bar').forEach(el => el.setAttribute('dir', direction));
     document.querySelectorAll('.sidebar').forEach(el => el.setAttribute('dir', direction));
+    // Apply per-category line-height override, or restore theme default
+    const lh = cat && cat['line-height'];
+    document.documentElement.style.setProperty('--line-height-body', lh ? String(lh) : (defaultLineHeight || '1.7'));
   }
 
   function doSearch(query, resultsEl) {
@@ -2770,6 +2774,7 @@ function fmtDatetime(dtStr) {
 
       if (config.theme) applyThemeYml(themeConfig);
       else applyConfigTheme();
+      defaultLineHeight = getComputedStyle(document.documentElement).getPropertyValue('--line-height-body').trim() || '1.7';
       applyTheme(getInitialTheme());
 
       // nav.yml — phase 2 expects `sections:` + `pages:` blocks; phase 1 flat