Naming, layout and comments: descriptive full-word names, one item per line in wrapped calls and literals, and doc comments on exported names

Short and single-letter names in application code become full words (tests
keep theirs). Wrapped calls, signatures and composite literals put one item
per line, and one-line function bodies are expanded. Exported names and
groups of constants get doc comments, and comments refer to the renamed
identifiers.

internal/mock/findatender/doc.go

@@ -6,8 +6,7 @@
 package mock
 
 // Files kept in the mock-data directory.
-//
-//	ReleasesFile is created and appended to by the mock.
 const (
+	// ReleasesFile is created and appended to by the mock.
 	ReleasesFile = "releases.jsonl"
 )