feat(cd): optionally complete from zoxide's database

`cd` completes from FileGenerator, which reads one directory: the one you
are standing in. So `cd proj` only ever resolves when proj happens to be
a child of the current directory, and returns nothing at all otherwise --
including for directories visited constantly. That is the opposite of
what cd is normally reached for, and it reads as completion being broken
rather than as a scope limit.

zoxide.extend-cd routes `cd` through the generator `z` already uses, so
local children are offered first and zoxide's frecency database fills in
everything else, reachable by name from anywhere.

Off by default: it shells out to zoxide, and offering absolute paths from
outside the current directory is a real change in what `cd` proposes.

The query is also cached for two seconds. Generators run on every
keystroke and `zoxide query -l` is a subprocess costing ~11ms here, which
is the whole redraw budget; the list only changes when the user changes
directory, so the window costs nothing. This applies to `z` and `zi` too,
which were paying it per keystroke already.

commands/fs/cd.go

@@ -3,6 +3,7 @@ package fs
 import (
 	"strings"
 
+	"github.com/versenilvis/iris/internal/config"
 	"github.com/versenilvis/iris/spec"
 )
 
@@ -12,6 +13,14 @@ func init() {
 		Description: "change directory",
 		MaxArgs:     0,
 		Generator: func(tokens []string, prefix string, partial string) []spec.Suggestion {
+			// The file generator only reads the current directory, so `cd proj`
+			// comes back empty unless its parent is where you already are --
+			// which is not how cd is typically used. zoxide.extend-cd folds in
+			// the frecency database that `z` already queries, making any
+			// directory zoxide has seen reachable by name from anywhere.
+			if config.Get().Zoxide.ExtendCd {
+				return ZoxideGenerator()(tokens, prefix, partial)
+			}
 			fullQuery := strings.Join(tokens[1:], " ")
 			return spec.FileGenerator("/")(tokens, prefix, fullQuery)
 		},