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/server/server_test.go

@@ -1,4 +1,4 @@
-package server
+package server_test
 
 import (
 	"context"
@@ -8,6 +8,7 @@ import (
 	"git.eeqj.de/sneak/routewatch/internal/config"
 	"git.eeqj.de/sneak/routewatch/internal/logger"
 	"git.eeqj.de/sneak/routewatch/internal/metrics"
+	"git.eeqj.de/sneak/routewatch/internal/server"
 	"git.eeqj.de/sneak/routewatch/internal/streamer"
 )
 
@@ -16,18 +17,31 @@ import (
 // listened in a goroutine, only logged the failure and returned nil, so the
 // daemon kept running without its web server.
 func TestStartFailsWhenPortIsHeld(t *testing.T) {
-	held, err := net.Listen("tcp", ":0")
+	t.Parallel()
+
+	var listenConfig net.ListenConfig
+
+	held, err := listenConfig.Listen(t.Context(), "tcp", ":0")
 	if err != nil {
 		t.Fatalf("failed to open the test listener: %v", err)
 	}
 	defer func() { _ = held.Close() }()
 
-	port := held.Addr().(*net.TCPAddr).Port
+	addr, ok := held.Addr().(*net.TCPAddr)
+	if !ok {
+		t.Fatalf("test listener address %v is not a TCP address", held.Addr())
+	}
+
+	port := addr.Port
 	log := logger.New()
-	s := New(nil, streamer.New(log, metrics.New()), log, &config.Config{Port: port})
+	s := server.New(nil, streamer.New(log, metrics.New()), log,
+		&config.Config{Port: port})
+
 	defer func() { _ = s.Stop(context.Background()) }()
 
-	if err := s.Start(); err == nil {
-		t.Fatalf("Start returned nil while port %d was held by another listener", port)
+	err = s.Start(t.Context())
+	if err == nil {
+		t.Fatalf("Start returned nil while port %d was held by another listener",
+			port)
 	}
 }