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.go

@@ -3,6 +3,7 @@ package server
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"net/http"
@@ -42,7 +43,12 @@ type Server struct {
 }
 
 // New creates a new HTTP server
-func New(db database.Store, streamer *streamer.Streamer, logger *logger.Logger, cfg *config.Config) *Server {
+func New(
+	db database.Store,
+	streamer *streamer.Streamer,
+	logger *logger.Logger,
+	cfg *config.Config,
+) *Server {
 	s := &Server{
 		db:       db,
 		streamer: streamer,
@@ -57,8 +63,8 @@ func New(db database.Store, streamer *streamer.Streamer, logger *logger.Logger,
 
 // Start listens on the configured port and serves HTTP in the background.
 // It returns an error if it cannot listen, for example because the port is
-// already in use.
-func (s *Server) Start() error {
+// already in use. ctx bounds only opening the port, not serving.
+func (s *Server) Start(ctx context.Context) error {
 	const (
 		network           = "tcp"
 		readHeaderTimeout = 40 * time.Second
@@ -78,7 +84,9 @@ func (s *Server) Start() error {
 
 	s.logger.Info("Starting HTTP server", "port", s.port, "addr", s.srv.Addr)
 
-	listener, err := net.Listen(network, s.srv.Addr)
+	var listenConfig net.ListenConfig
+
+	listener, err := listenConfig.Listen(ctx, network, s.srv.Addr)
 	if err != nil {
 		return fmt.Errorf("starting HTTP server: %w", err)
 	}
@@ -86,7 +94,8 @@ func (s *Server) Start() error {
 	s.logger.Info("HTTP server listening", "addr", listener.Addr().String())
 
 	go func() {
-		if err := s.srv.Serve(listener); err != nil && err != http.ErrServerClosed {
+		err := s.srv.Serve(listener)
+		if err != nil && !errors.Is(err, http.ErrServerClosed) {
 			s.logger.Error("HTTP server error", "error", err)
 		}
 	}()