Re-vendor the shared files from sneak/prompts at dd4027b (closes #52)

Takes .golangci.yml, .dockerignore, .gitignore, .editorconfig, the
workflow and REPO_POLICIES.md from sneak/prompts dd4027b, keeping this
repository's own entries after the shared content. Lint (golangci-lint
v2.14.0) and test become Dockerfile phases that script/lint and
script/test build alone and uncached; the image build depends on both,
and script/cibuild bootstraps, runs script/check, then builds the image.
The agent guidance file moves to AGENTS.md. The Go code is fixed for
what the new configuration finds; reads that iterate rows now also
report an iteration error.

Model: opus-5-5

internal/logger/logger.go

@@ -74,6 +74,7 @@ func getSourceAttrs() []slog.Attr {
 
 	// Get the function name
 	fn := runtime.FuncForPC(pc)
+
 	var funcName string
 	if fn != nil {
 		funcName = filepath.Base(fn.Name())