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

pkg/asinfo/asinfo.go

@@ -1,4 +1,3 @@
-// Package asinfo provides information about Autonomous Systems (AS)
 package asinfo
 
 import (
@@ -54,7 +53,9 @@ func initRegistry() {
 	}
 
 	var asInfos []Info
-	if err := json.Unmarshal(jsonData, &asInfos); err != nil {
+
+	err = json.Unmarshal(jsonData, &asInfos)
+	if err != nil {
 		panic("failed to unmarshal embedded AS data: " + err.Error())
 	}
 
@@ -137,6 +138,7 @@ func Search(query string) []Info {
 	defer defaultRegistry.mu.RUnlock()
 
 	var results []Info
+
 	for _, info := range defaultRegistry.byASN {
 		if contains(info.Handle, query) || contains(info.Description, query) {
 			results = append(results, *info)