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/expiry.go

@@ -4,7 +4,6 @@ import (
 	"time"
 
 	"git.kebcloud.no/keb/lazysecrets/internal/expiry"
-
 	"git.kebcloud.no/keb/lazysecrets/internal/provider"
 )
 
@@ -12,30 +11,19 @@ import (
 // list once they have expired (✗ expired) or will within the configured
 // warning period (⚠ 12d), and typing "expir" in the filter finds them.
 
-type expiryState = expiry.State
-
-const (
-	notExpiring = expiry.None
-	expiresSoon = expiry.Soon
-	expired     = expiry.Expired
-)
-
 // expiry tells whether o has expired or will within the warning period,
 // and how long it has left.
-func (m Model) expiry(o provider.Object) (expiryState, time.Duration) {
+func (m Model) expiry(o provider.Object) (expiry.State, time.Duration) {
 	return expiry.Of(o.Expires, m.now(), m.expiryWarning)
 }
 
 // expiryWord is matched by the filter: "expired" or "expiring".
 func (m Model) expiryWord(o provider.Object) string {
 	switch state, _ := m.expiry(o); state {
-	case expired:
+	case expiry.Expired:
 		return "expired"
-	case expiresSoon:
+	case expiry.Soon:
 		return "expiring"
 	}
 	return ""
 }
-
-// daysLeft is a short "12d", or "5h" on the last day.
-func daysLeft(d time.Duration) string { return expiry.Left(d) }