refactor: drop dead code and use the standard library where it already does the job (#76)

No behaviour change.

- Deleted, unused or one-line wrappers: panes.RuneIndexes, Detail.Refresh (SetDescribed does it), SecretValue.Len, Query.Empty, Clipboard.Native, config.Load, get's value, Model.done, providerOf (cachefile.ProviderOf), contextWithTimeout, searchCoverage, startCrawl, showKeybindings, the expiry aliases and daysLeft.
- cmp.Or instead of the two cmpOr copies; slices.Sorted(maps.Keys(…)), maps.Copy, wg.Go, utf8.RuneCountInString and new(true) instead of loops and helpers that do the same.
- A container's pane title is set once, not twice; a redundant length check in share links and a no-op assignment in linkhandler.Launch are gone.
- Tests call ansi.Strip and lastLines directly; gofmt -s on links.go.

Reviewed-on: #76
Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>

internal/ui/app/notes_test.go

@@ -77,17 +77,15 @@ func TestNotesOnRows(t *testing.T) {
 func TestWithNoteGivesWay(t *testing.T) {
 	t.Parallel()
 	st := styles.Default()
-	if got := withNote(st, "db-password", "prod SQL admin", 30); len([]rune(stripANSI(got))) != 30 ||
-		!strings.HasSuffix(stripANSI(got), "prod SQL admin") {
-		t.Errorf("fits: %q", stripANSI(got))
+	if got := withNote(st, "db-password", "prod SQL admin", 30); len([]rune(ansi.Strip(got))) != 30 ||
+		!strings.HasSuffix(ansi.Strip(got), "prod SQL admin") {
+		t.Errorf("fits: %q", ansi.Strip(got))
 	}
-	if got := stripANSI(withNote(st, "db-password", "prod SQL admin", 20)); !strings.HasPrefix(got, "db-password") ||
+	if got := ansi.Strip(withNote(st, "db-password", "prod SQL admin", 20)); !strings.HasPrefix(got, "db-password") ||
 		!strings.HasSuffix(got, "…") {
 		t.Errorf("tight: %q", got)
 	}
-	if got := stripANSI(withNote(st, "a-very-long-secret-name", "note", 20)); got != "a-very-long-secret-name" {
+	if got := ansi.Strip(withNote(st, "a-very-long-secret-name", "note", 20)); got != "a-very-long-secret-name" {
 		t.Errorf("no room: %q", got)
 	}
 }
-
-func stripANSI(s string) string { return ansi.Strip(s) }