docs(man): backfill man pages with wiki-only info (source-of-truth pass)

Port information that previously lived only in the GitHub wiki into the
authoritative scdoc man pages, so the man pages become the single source
of truth for module documentation.

33 man pages enriched (options, format replacements, actions, style
selectors, troubleshooting and implementation notes). Additions were
verified against the source; stale/incorrect wiki entries were
deliberately not ported. All pages still compile with scdoc.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

man/waybar-image.5.scd

@@ -100,6 +100,29 @@ $path\\n$tooltip
 }
 ```
 
+Using *exec* to fetch the image via a script:
+
+```
+"image#album-art": {
+	"exec": "~/.config/waybar/custom/spotify/album_art.sh",
+	"size": 32,
+	"interval": 30
+}
+```
+
+Where *album\_art.sh* looks like this:
+
+```
+#!/bin/bash
+album_art=$(playerctl -p spotify metadata mpris:artUrl)
+if [[ -z $album_art ]]; then
+	# spotify is dead, we should die too.
+	exit
+fi
+curl -s "${album_art}" --output "/tmp/cover.jpeg"
+echo "/tmp/cover.jpeg"
+```
+
 # STYLE
 
 - *#image*