Remove the open command

`open` and `view` shared one implementation and differed in a single
line: `open` also made the project the active one. Only `view` is left,
with the behaviour it always had.

Dropping it from builtinCmds is the part worth noting: a reserved word
cannot be shadowed by an alias, so `open` is now free for one --
`alias open '!xdg-open $1'` works, which it could not before. That also
made a completion test wrong, since it used `open` as its example of a
name a builtin owns; it uses `status` now.

The `runInDir(d, "open", ...)` calls stay: those are macOS's open(1),
which is how an Xcode workspace gets opened.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

commands.go

@@ -573,7 +573,7 @@ func runCommandDepth(line string, depth int) bool {
 			}
 		}
 
-	case "open", "view": // open project in Xcode / editor
+	case "view": // open a project in Xcode / the configured editor
 		prj := PRJ
 		if w := word(words, 1); w != "" {
 			prj = w
@@ -608,9 +608,6 @@ func runCommandDepth(line string, depth int) bool {
 			}
 			runInDir(d, editor, d)
 		}
-		if words[0] == "open" {
-			PRJ = prj
-		}
 
 	case "count": // count source lines in the project
 		if !requireProject() {
@@ -809,7 +806,7 @@ const gitignore = `.DS_Store
 
 var helpItems = []struct{ cmd, desc string }{
 	{"cd [project]", "change project (no argument: back to the base)"},
-	{"open [project]", "open project"},
+	{"view [project]", "open project in Xcode / the editor"},
 	{"init", "make new repository from current directory"},
 	{"push [comment]", "push changes to git server"},
 	{"pushremote [@name] [desc]", "mirror repo to the public server(s) (gitea/github/gitlab)"},