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/ristypes/ris.go

@@ -1,4 +1,5 @@
-// Package ristypes defines the data structures for RIS Live BGP messages and announcements.
+// Package ristypes defines the data structures for RIS Live BGP messages and
+// announcements.
 package ristypes
 
 import (
@@ -17,25 +18,30 @@ type ASPath []int
 func (p *ASPath) UnmarshalJSON(data []byte) error {
 	// First try to unmarshal as a simple array of integers
 	var simple []int
-	if err := json.Unmarshal(data, &simple); err == nil {
+
+	err := json.Unmarshal(data, &simple)
+	if err == nil {
 		*p = ASPath(simple)
 
 		return nil
 	}
 
 	// If that fails, unmarshal as array of interfaces and flatten
-	var raw []interface{}
-	if err := json.Unmarshal(data, &raw); err != nil {
+	var raw []any
+
+	err = json.Unmarshal(data, &raw)
+	if err != nil {
 		return err
 	}
 
 	// Flatten the array
 	result := make([]int, 0)
+
 	for _, item := range raw {
 		switch v := item.(type) {
 		case float64:
 			result = append(result, int(v))
-		case []interface{}:
+		case []any:
 			// Nested array - flatten it
 			for _, nested := range v {
 				if num, ok := nested.(float64); ok {
@@ -62,6 +68,8 @@ type RISLiveMessage struct {
 // It contains metadata about the BGP session (peer, ASN, host) along with
 // the actual BGP update data including AS path, communities, announcements,
 // and withdrawals.
+//
+//nolint:tagliatelle // field names are the RIS Live feed's
 type RISMessage struct {
 	Type            string    `json:"type"`
 	Timestamp       float64   `json:"timestamp"`
@@ -90,6 +98,8 @@ type RISMessage struct {
 // RISAnnouncement represents a BGP route announcement within a RIS message.
 // It contains the next hop IP address and the list of prefixes being announced
 // via that next hop.
+//
+//nolint:tagliatelle // field names are the RIS Live feed's
 type RISAnnouncement struct {
 	NextHop  string   `json:"next_hop"`
 	Prefixes []string `json:"prefixes"`