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/edit.go

@@ -242,7 +242,7 @@ func (m *Model) openInEditor(f provider.File, finished func(error) tea.Msg) tea.
 			return tea.QuitMsg{}
 		}
 	}
-	if editor := cmpOr(m.getenv("VISUAL"), m.getenv("EDITOR")); editor != "" {
+	if editor := cmp.Or(m.getenv("VISUAL"), m.getenv("EDITOR")); editor != "" {
 		// Through the shell, so EDITOR can carry arguments ("code -w").
 		args := append([]string{"-c", editor + ` "$@"`, "lazysecrets"}, editorArgs(editor, f)...)
 		m.flash = flash{}