Fix linting issues: canonicalheader, embeddedstructfieldcheck, iotamixing, makezero, testableexamples, wastedassign, usetesting, tparallel, unconvert, intrange, iface

- canonicalheader: fix cacheTTL header value to canonical form
- embeddedstructfieldcheck: move embedded fields before regular fields in 4 structs
- iotamixing: split const blocks mixing iota with non-iota constants
- makezero: use make([]T, 0, n) instead of make([]T, n) before appending
- testableexamples: add missing Output: comment to ExampleOption_UnwrapOrZero
- wastedassign: remove wasted initial assignments in 4 locations
- usetesting: replace os.MkdirTemp/os.Setenv with t.TempDir/t.Setenv in tests
- tparallel: add t.Parallel() to 8 top-level test functions
- unconvert: remove 16 unnecessary type conversions
- intrange: convert 3 for loops to use integer range syntax
- iface: consolidate identical EditPrompter and Prompt interfaces via type alias

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

pkg/cmd/extension/extension.go

@@ -74,7 +74,7 @@ func (e *Extension) URL() string {
 		}
 	case GitKind:
 		if remoteURL, err := e.gitClient.Config("remote.origin.url"); err == nil {
-			url = strings.TrimSpace(string(remoteURL))
+			url = strings.TrimSpace(remoteURL)
 		}
 	}
 
@@ -196,7 +196,7 @@ func (e *Extension) Owner() string {
 		}
 	case GitKind:
 		if remoteURL, err := e.gitClient.Config("remote.origin.url"); err == nil {
-			if url, err := git.ParseURL(strings.TrimSpace(string(remoteURL))); err == nil {
+			if url, err := git.ParseURL(strings.TrimSpace(remoteURL)); err == nil {
 				if repo, err := ghrepo.FromURL(url); err == nil {
 					owner = repo.RepoOwner()
 				}