docs: add missing per-category config keys to reference-config.md

Documents all keys that can appear under default-category and
categories entries: message, name-latin, notfoundmessage,
pagenotfoundmessage, font, and line-height. Adds a summary table
and updates the full example to show these keys in context.

docs/reference-config.md

@@ -151,16 +151,40 @@ categories-use: yes            # Enable the category system. Default: no.
 
 default-category:              # The category used when no ?cat= parameter is in the URL.
   code: en                     # Short code. Used in filenames (page.en.md) and URL params.
-  name: English                # Display name shown in the category selector.
+  name: English                # Display name shown in the category dropdown list.
+  message: English             # Label shown on the selector bar (trigger button). Falls back to name.
+  name-latin: English          # Secondary label shown in the dropdown alongside name. Use when name
+                               # is in a non-Latin script (e.g. Arabic, Devanagari) to aid recognition.
+                               # Omit if name is already Latin or identical to name.
   direction: ltr               # Text direction. ltr or rtl. Default: ltr.
+                               # rtl flips the nav position and content text direction.
+  notfoundmessage: "Not available in this language"
+                               # Short note shown in the dropdown when no variant exists for the
+                               # current page. Also enables fallback: the renderer will fall back to
+                               # the default-category content instead of hiding the page.
+                               # Omit to hide the category from the dropdown when no variant exists.
+  pagenotfoundmessage: "This page is not yet available in English."
+                               # Message shown in the content area when a page cannot be fetched for
+                               # this category. Overrides the top-level pagenotfoundmessage.
+  font: NotoNastaliqUrdu-Regular.ttf
+                               # Font filename inside assets/fonts/. Loaded on demand when this
+                               # category is activated. Useful for scripts that need a specific font.
+  line-height: 2.8             # Line height override for this category. Useful for scripts like
+                               # Nastaliq that need extra vertical space. Restores to theme default
+                               # when switching away.
 
-categories:                    # Additional categories.
+categories:                    # Additional categories. Each entry supports the same keys as
+                               # default-category above.
   - code: nb
     name: Norsk
     direction: ltr
   - code: ar
     name: عربي
-    direction: rtl             # RTL flips nav position and content text direction.
+    name-latin: Arabic
+    direction: rtl
+    notfoundmessage: "غير متاح"
+    font: NotoNastaliqUrdu-Regular.ttf
+    line-height: 2.8
 
 categories-sectionnames: same  # How section names are shown per category.
                                # same: all categories share one section name (defaultname in nav.yml).
@@ -170,6 +194,20 @@ categories-selecticon: globe   # Icon shown in the category selector bar. SVG na
 categories-selecttext: "Language"  # Label shown next to the icon in the category selector bar.
 ```
 
+### Per-category keys summary
+
+| Key | Required | Description |
+|---|---|---|
+| `code` | Yes | Short identifier used in filenames (`page.nb.md`) and the `?cat=` URL param. |
+| `name` | Yes | Display name shown in the dropdown list. |
+| `message` | No | Label shown on the selector trigger button. Falls back to `name`. |
+| `name-latin` | No | Secondary label in the dropdown, shown alongside `name` when `name` uses a non-Latin script. |
+| `direction` | No | `ltr` or `rtl`. Default: `ltr`. RTL flips nav and content direction. |
+| `notfoundmessage` | No | Short note shown in the dropdown when no variant exists for the current page. Also enables fallback to default-category content. |
+| `pagenotfoundmessage` | No | Message shown in the content area when a page cannot be fetched for this category. Overrides the top-level `pagenotfoundmessage`. |
+| `font` | No | Font filename from `assets/fonts/`. Loaded on demand when this category is activated. |
+| `line-height` | No | Body line height override for this category. Restores to theme default when switching away. |
+
 ---
 
 ## Reusable callout messages
@@ -228,6 +266,29 @@ offline-message:
   nb: "Du er frakoblet. Koble til og last inn på nytt."
 
 language: en
+pagenotfoundmessage: "Please select a page to continue."
+
+categories-use: yes
+default-category:
+  code: en
+  name: English
+  direction: ltr
+categories:
+  - code: nb
+    name: Norsk
+    direction: ltr
+    notfoundmessage: "Ikke tilgjengelig på norsk"
+  - code: ar
+    name: عربي
+    name-latin: Arabic
+    direction: rtl
+    notfoundmessage: "غير متاح"
+    pagenotfoundmessage: "هذه الصفحة غير متاحة."
+    font: NotoNastaliqUrdu-Regular.ttf
+    line-height: 2.8
+categories-sectionnames: same
+categories-selecticon: globe
+categories-selecttext: "Language"
 
 callouts:
   aitranslation: