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/fetcher/worker_sleeper.go

@@ -15,10 +15,13 @@ const sleepDuration = 60 * time.Second
 // runSleeper runs the sleeper test source until ctx is cancelled: every
 // configured interval it simulates work by sleeping for sleepDuration.
 func runSleeper(
-	ctx context.Context, logger *slog.Logger, conf *config.JobSearchConfig, since time.Time,
+	ctx context.Context,
+	logger *slog.Logger,
+	conf *config.JobSearchConfig,
+	since time.Time,
 ) error {
 	blockShutdown := conf.Sources.Sleeper.BlockShutdown
-	w := util.Worker{
+	worker := util.Worker{
 		Logger:   logger,
 		Name:     "Sleeper",
 		Interval: conf.Sources.Sleeper.Interval,
@@ -30,7 +33,7 @@ func runSleeper(
 			}
 		},
 	}
-	return w.Run(ctx, since)
+	return worker.Run(ctx, since)
 }
 
 // sleep simulates work taking duration, returning early with ctx.Err() if ctx