refactor: remove features beyond the UX plan

Drop additions that the UX plan does not ask for:

- the interactive label edit form; label edit now requires a flag
- label clone and the skip mode of label creation it needed
- repo rename rewriting the Git remote or tea.repository; it now
  warns that the remote still points to the old name
- the extra "source" remote on clones of pull mirrors
- run artifact download, which duplicates run download --zip
- 256-color and 24-bit label swatches; colors stay ANSI 16
- config list --show-source (config get keeps it)
- the membership and access GETs before team member/repo add and
  remove; Gitea's PUT and DELETE are idempotent

label edit/delete keep --by-name: it is the only way to address a
label whose name is a number that is also another label's ID.

Signed-off-by: bircni <bircni@icloud.com>

internal/terminal/view_test.go

@@ -52,8 +52,8 @@ func TestViewRender(t *testing.T) {
 		{
 			"styled for color terminals",
 			View{Title: "v1.0", Badges: []Cell{{Text: "Latest", Color: "green"}}, Fields: []Field{{Label: "Labels", Cells: []Cell{{Text: "bug", Color: "ee0701"}}}}, URL: "https://example.org/r"},
-			Display{TTY: true, Color: true, TrueColor: true},
-			"\x1b[1mv1.0\x1b[0m\n\x1b[32mLatest\x1b[0m\n\x1b[1mLabels:\x1b[0m \x1b[38;2;238;7;1mbug\x1b[0m\n\n" +
+			Display{TTY: true, Color: true},
+			"\x1b[1mv1.0\x1b[0m\n\x1b[32mLatest\x1b[0m\n\x1b[1mLabels:\x1b[0m bug\n\n" +
 				"\x1b[90mNo description provided\x1b[0m\n\n\x1b[90mView on Gitea: https://example.org/r\x1b[0m\n",
 		},
 		{