refactor: drop dead code and use the standard library where it already does the job

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.

internal/commands/commands.go

@@ -16,6 +16,7 @@
 package commands
 
 import (
+	"cmp"
 	"fmt"
 	"regexp"
 	"strings"
@@ -60,10 +61,7 @@ var envName = regexp.MustCompile(`^[A-Za-z_][A-Za-z0-9_]*$`)
 
 // Validate checks a command from the config.
 func (c Command) Validate() error {
-	name := c.Description
-	if name == "" {
-		name = c.Command
-	}
+	name := cmp.Or(c.Description, c.Command)
 	switch {
 	case c.Command == "":
 		return fmt.Errorf("custom command %q has no command", c.Description)