feat(editor/vertico): improve extension setup

Override default straight recipe for vertico to expose extensions as
packages.

Also create hacky vertico-directory-mode to easily toggle
vertico-directory features on and off.

vertico-directory-mode is then used by a projectile advice to
temporarily disable vertico-directory features while completing results
from projectile. This is required to avoid breaking the
projectile-switch-project and related commands, as the project list is
not a set of files, but vertico-directory-enter thinks it is.

core/siren-core-package-overrides.el

@@ -12,7 +12,21 @@
                 ;; package on elpa.gnu.org is quite old.
                 (undo-tree :type git :host gitlab
                            :repo "tsc25/undo-tree"
-                           :branch "master")))))
+                           :branch "master")
+                ;; Override vertico recipe to fix issues with extensions.
+                (vertico :type git :host github :repo "minad/vertico"
+                         :files (:defaults "extensions/*")
+                         :includes (vertico-buffer
+                                    vertico-directory
+                                    vertico-flat
+                                    vertico-grid
+                                    vertico-indexed
+                                    vertico-mouse
+                                    vertico-multiform
+                                    vertico-quick
+                                    vertico-repeat
+                                    vertico-reverse
+                                    vertico-unobtrusive))))))
 
 (provide 'siren-core-package-overrides)
 ;;; siren-core-packages.el ends here