chore(kb/cron): add warning about quoting the percent char

knowledge base/cron.md

@@ -31,6 +31,8 @@ All crontab files:
 - Must be either regular files or symlinks to regular files.
 - Must **not** be executable **nor** writable for anyone else but the owner.<br/>
   This requirement can be overridden by using the `-p` option on `crond`'s command line.
+- Must escape the `%` character in commands, if used (e.g., in `date`'s formatting).<br/>
+  Cron interprets `%` as a newline. Everything after it is sent to the command's stdin, not as part of the command.
 
 > [!important]
 > If `inotify` support is in use, changes in symlinked crontabs are **not** automatically noticed by the cron daemon.

knowledge base/crontab.md

@@ -6,6 +6,10 @@
 
 ## TL;DR
 
+> [!caution]
+> Escape the `%` character if used in commands (e.g., in `date`'s formatting), even if in quotes.<br/>
+> Cron interprets `%` as a newline. Everything after it is sent to the command's stdin, not as part of the command.
+
 ```sh
 # List existing jobs.
 crontab -l
@@ -35,7 +39,9 @@ sudo crontab -r -u 'nana'
 */10 * * * * ls
 
 # Run a script at 02:34 every Friday.
+# `%` needs escaping even in quotes
 34 2 * * Fri /absolute/path/to/script.sh
+35 3 * * FRI /absolute/path/to/script.sh > /absolute/path/to/script.$(date '+\%F').log
 ```
 
 ## Further readings