docs(feed): add the cover image to the special missings post

Cover art for "28 Ways to Be Missing in SAS": a pack of wolves on a snow plain
at dusk with one animal standing apart, carrying the post's opening line - a
numeric missing is not a lone wolf, there are 28 of them.

Source image was 4:3, so it is cropped to 1.91:1 (1200x627) to match the other
feed covers and double as the LinkedIn share card. The crop was chosen to keep
both the lone wolf on the left and the full pack on the right in frame, losing
only sky above the clouds and foreground snow.

Sets previewImg in the front matter; the template renders it, so it is not
embedded in the body as well. Verified through gatsby build - the image
pipeline emits 300/600/1200-wide variants.

content/blog/v4-0-formats-special-missings/index.md

@@ -61,7 +61,7 @@ Did you know that, in addition to a regular missing value in SAS (`.`), there ar
 
 These values can now be both viewed and edited in Data Controller following an update to the [SASjs Adapter](https://github.com/sasjs/adapter#variable-types).
 
-`video: [Retain Formulas when Loading Excel to SAS](https://www.youtube-nocookie.com/embed/ggrcNr23Jzw)`
+`video: [Managing Special Missing Values with Data Controller for SAS](https://www.youtube-nocookie.com/embed/ggrcNr23Jzw)`
 
 There is nothing extra to configure for special SAS numerics - they are simply available by default, for numeric cells.
 

content/feed/sas-special-missings/index.md

@@ -7,6 +7,7 @@ authorLink: https://www.linkedin.com/in/allanbowe/
 tags:
   - Special Missings
   - Data Quality
+previewImg: './cover.jpeg'
 ---
 
 # 28 Ways to Be Missing in SAS
@@ -90,5 +91,32 @@ The video shows the whole cycle - entering them, the rejections, submit, approve
 
 #sas #datacapture #mdm #dataquality
 
-Image prompt: a pack of 28 wolves fanning out across a snowy plain at dusk, one wolf standing apart to the left, wide cinematic composition, cool blue-grey palette with a single warm amber accent on the lone wolf, soft depth of field, no text and no logos, 16:9, editorial cover art for a technical blog post about the 28 SAS missing values. Save the generated image as ./cover.jpeg and set previewImg: './cover.jpeg' in the front matter above.
+Image prompt: Cinematic editorial cover illustration: a large pack of wolves, a
+dozen or more, spread wide and moving together across a vast snow plain at dusk,
+seen from a low wide angle. One wolf stands apart from the group on the left of
+frame, turned back toward the pack. The pack is rendered in cool blue-grey and
+silver; the lone wolf catches the only warm light in the scene, a single low
+amber sun. Overcast dusk sky, faint falling snow, long soft shadows, generous
+empty sky and snow to the upper third so the wide crop breathes. Painterly
+digital illustration, muted desaturated palette, soft depth of field with the
+distant wolves falling out of focus, no text, no letters, no numbers, no logos,
+no watermark.
+
+Constraints: no text, no letters, no numbers, no digits, no symbols, no
+captions, no logos, no watermark, no signature, no border, no frame, no collar,
+no harness, no humans, no buildings, and do not ask for an exact head count of
+28 - a crowded pack reads worse than a dozen clear animals, and the number
+belongs in the headline, not the artwork. The no-text rule matters more than
+usual here: the subject is letters standing in for numbers, so a stray glyph
+anywhere undercuts the cover.
+
+Output: save as ./cover.jpeg at 1.91:1 (1200x627, matching the other feed
+covers and doubling as the LinkedIn share card), and set
+previewImg: './cover.jpeg' in the front matter above. Do not also embed the
+image in the markdown body. Full prompt, variants and rationale:
+https://paste.4gl.io/?513711f5bde3610e#9LZCA9xzQHDy3CycXmsWU5AoVNtjBZmPotUHHtHTAerF
+
+Fallback variant if the pack composition comes back muddled: a single wolf
+standing alone on a snow plain at dusk, its shadow stretching toward a distant
+pack reduced to small silhouettes on the horizon.
 -->