feat(emacs): Fill some search-related stubs

README.org

@@ -643,6 +643,29 @@ Run various checks on the system.
 
 List persistent files per user, and show their mount strategy.
 
+- Show info about ~sydnix.impermanence.cache~ values. Extend that option to have "description" and "consequences" fields, which are shown to users before clearing them. e.g.
+
+  #+begin_src nix
+  {
+    sydnix.impermanence.cache.directories.".local/share/emacs/cache" = {
+      description = "Root of all caches for Emacs and Emacs packages.";
+      consequences = [
+        "All known projects will be forgotten"
+        "All trusted .dir-locals.el files and values will be forgotten"
+      ];
+    };
+  }
+  #+end_src
+
+  #+begin_example
+ $ sydnix cache clear
+ Recursively remove `~/.local/share/emacs/cache'?
+ - All known projects will be forgotten
+ - All trusted .dir-locals.el files and values will be forgotten
+[y/n]
+«more caches…»
+  #+end_example
+
 * References
 
 Following is a subset of the many places I've learnt from. Most important of all are Doom Emacs and Faye's Wishsys.