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>

api/client.go

@@ -19,7 +19,7 @@ const (
 	apiVersion      = "X-GitHub-Api-Version"
 	apiVersionValue = "2022-11-28"
 	authorization   = "Authorization"
-	cacheTTL        = "X-GH-CACHE-TTL"
+	cacheTTL        = "X-Gh-Cache-Ttl"
 	graphqlFeatures = "GraphQL-Features"
 	features        = "merge_queue"
 	userAgent       = "User-Agent"
@@ -46,6 +46,7 @@ type GraphQLError struct {
 
 type HTTPError struct {
 	*ghAPI.HTTPError
+
 	scopesSuggestion string
 }