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/metrics/metrics_test.go

@@ -1,12 +1,18 @@
-package metrics
+package metrics_test
 
-import "testing"
+import (
+	"testing"
+
+	"git.eeqj.de/sneak/routewatch/internal/metrics"
+)
 
 // TestReconnectCount connects three times with a disconnect between each, the
 // way the streamer does, and expects every connection after the first to count
 // one reconnect.
 func TestReconnectCount(t *testing.T) {
-	tracker := New()
+	t.Parallel()
+
+	tracker := metrics.New()
 
 	tracker.SetConnected(true)
 	tracker.SetConnected(false)