#19: fix F1-F3 defects found auditing the phases against PLAN.md

Every fix here is a case where the code and the plan disagreed, and the
code was wrong.

Certificates (section 8.2, 8.4). The parser documented that it skipped
expired entries but never checked, so an expired certificate would be
served until every handshake failed. LastReload() only advanced when
acme.json changed - and it does not change for sixty days - which made
the timestamp risk R2 monitors indistinguishable from a watcher gone
blind. Expiry is now checked on every pass, LastReload records the check
and LastChange the swap, and the <7d/<24h alerts of section 8.4 exist.

ARC (section 5). buildArcSealer resolved the DKIM key at startup, before
runDnsReconciler had provisioned one. On a first boot ARC was disabled
until someone restarted the process, which the log even admitted while
offering no way for it to start. A LazySealer binds on first use instead.

Health (section 8.4). There was no degraded state at all. /health now
reports one - still 200, because restarting cannot fix a certificate
Traefik never issued.

Bounces. DSNs were sent From postmaster@lambdamail.local, a domain that
does not resolve, so the notification was itself undeliverable. They now
carry the configured mail host, a Message-ID, and Auto-Submitted so a
vacation responder cannot loop against them.

Fan-out atomicity (section 6.1). Persist ran one transaction per
recipient, so a failure halfway through an alias fan-out left earlier
recipients with a copy while the sender was told to retry - and the retry
delivered to them twice. PersistAll commits the whole delivery or none of
it. Verified against Postgres by reverting the repository to the old
behaviour and confirming the new test fails on it.

SMTP replies. The use case encoded replies in error text ("550 5.7.1 ...")
which the adapter re-parsed by prefix, so rewording a message could turn a
permanent refusal into a retry. SmtpRejection carries the decision and the
adapter renders it.

Repository tests. These only run with TEST_DATABASE_URL, which CI does
set - so the job was red: copy and expunge seeded a 68-character digest
into a CHAR(64) column, and three others used fixed digests that collide
with the UNIQUE index on any re-run. A shared testBlobDigest() helper
fixes both; the suite now passes twice in a row against one database.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

services/protocols/internal/infrastructure/tls/acme_cert_watcher_test.go

@@ -20,6 +20,13 @@ import (
 // makeCertPEM issues a self-signed certificate for the given names.
 func makeCertPEM(t *testing.T, names ...string) (certPEM, keyPEM []byte) {
 	t.Helper()
+	return makeCertPEMWithValidity(t, -time.Hour, 90*24*time.Hour, names...)
+}
+
+// makeCertPEMWithValidity issues a certificate whose validity window is given
+// relative to now, so a test can produce an expired or nearly expired one.
+func makeCertPEMWithValidity(t *testing.T, notBefore, notAfter time.Duration, names ...string) (certPEM, keyPEM []byte) {
+	t.Helper()
 
 	key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
 	if err != nil {
@@ -29,8 +36,8 @@ func makeCertPEM(t *testing.T, names ...string) (certPEM, keyPEM []byte) {
 		SerialNumber: big.NewInt(time.Now().UnixNano()),
 		Subject:      pkix.Name{CommonName: names[0]},
 		DNSNames:     names,
-		NotBefore:    time.Now().Add(-time.Hour),
-		NotAfter:     time.Now().Add(90 * 24 * time.Hour),
+		NotBefore:    time.Now().Add(notBefore),
+		NotAfter:     time.Now().Add(notAfter),
 	}
 	der, err := x509.CreateCertificate(rand.Reader, template, template, &key.PublicKey, key)
 	if err != nil {
@@ -49,6 +56,13 @@ func makeCertPEM(t *testing.T, names ...string) (certPEM, keyPEM []byte) {
 // resolver name to that resolver's account and certificates.
 func writeAcmeStore(t *testing.T, dir, resolverName string, entries map[string][]string) string {
 	t.Helper()
+	return writeAcmeStoreWithValidity(t, dir, resolverName, entries, -time.Hour, 90*24*time.Hour)
+}
+
+// writeAcmeStoreWithValidity is writeAcmeStore with control over how long the
+// issued certificates are valid for.
+func writeAcmeStoreWithValidity(t *testing.T, dir, resolverName string, entries map[string][]string, notBefore, notAfter time.Duration) string {
+	t.Helper()
 
 	type domain struct {
 		Main string   `json:"main"`
@@ -62,7 +76,7 @@ func writeAcmeStore(t *testing.T, dir, resolverName string, entries map[string][
 
 	var certificates []certificate
 	for main, sans := range entries {
-		certPEM, keyPEM := makeCertPEM(t, append([]string{main}, sans...)...)
+		certPEM, keyPEM := makeCertPEMWithValidity(t, notBefore, notAfter, append([]string{main}, sans...)...)
 		certificates = append(certificates, certificate{
 			Domain:      domain{Main: main, SANs: sans},
 			Certificate: base64.StdEncoding.EncodeToString(certPEM),
@@ -240,21 +254,63 @@ func TestAcmeCertWatcher_FailsWhenStoreMissing(t *testing.T) {
 	}
 }
 
-// An identical file must not cause a pointless swap; LastReload only advances
-// when the content actually changed.
-func TestAcmeCertWatcher_SkipsReloadWhenContentUnchanged(t *testing.T) {
+// An identical file must not cause a pointless swap, but the watcher must
+// still record that it looked. acme.json sits untouched for sixty days, so a
+// LastReload that only advanced on change could not tell a healthy idle
+// watcher apart from one that went blind (PLAN.md risk R2).
+func TestAcmeCertWatcher_SkipsSwapButRecordsCheckWhenContentUnchanged(t *testing.T) {
 	dir := t.TempDir()
 	writeAcmeStore(t, dir, "letsencrypt", map[string][]string{"mail.example.test": nil})
 
 	watcher, _ := NewAcmeCertWatcher(dir, "acme.json", "mail.example.test")
-	first := watcher.LastReload()
+	firstReload := watcher.LastReload()
+	firstChange := watcher.LastChange()
 
 	time.Sleep(2 * time.Millisecond)
 	if err := watcher.reload(); err != nil {
 		t.Fatalf("reload: %v", err)
 	}
 
-	if !watcher.LastReload().Equal(first) {
-		t.Error("an unchanged file triggered a reload")
+	if !watcher.LastChange().Equal(firstChange) {
+		t.Error("an unchanged file swapped the certificate store")
+	}
+	if !watcher.LastReload().After(firstReload) {
+		t.Error("LastReload did not advance, so a blind watcher would look identical to an idle one")
+	}
+}
+
+// An expired entry must not be served: every peer would reject the handshake,
+// whereas skipping it lets the SNI fallback take over (PLAN.md section 8.2).
+func TestAcmeCertWatcher_SkipsExpiredCertificate(t *testing.T) {
+	dir := t.TempDir()
+	writeAcmeStoreWithValidity(t, dir, "letsencrypt",
+		map[string][]string{"expired.example.test": nil}, -48*time.Hour, -24*time.Hour)
+
+	if _, err := NewAcmeCertWatcher(dir, "acme.json", "expired.example.test"); err == nil {
+		t.Fatal("a store holding only an expired certificate must not load as usable")
+	}
+}
+
+// The soonest expiry is what decides when the deployment breaks, so it has to
+// be readable for the alerts of PLAN.md section 8.4.
+func TestAcmeCertWatcher_ReportsEarliestExpiry(t *testing.T) {
+	dir := t.TempDir()
+	writeAcmeStoreWithValidity(t, dir, "letsencrypt",
+		map[string][]string{"mail.example.test": nil}, -time.Hour, 72*time.Hour)
+
+	watcher, err := NewAcmeCertWatcher(dir, "acme.json", "mail.example.test")
+	if err != nil {
+		t.Fatalf("NewAcmeCertWatcher: %v", err)
+	}
+
+	host, expiry, ok := watcher.EarliestExpiry()
+	if !ok {
+		t.Fatal("EarliestExpiry reported nothing for a loaded store")
+	}
+	if host != "mail.example.test" {
+		t.Errorf("EarliestExpiry host = %q, want mail.example.test", host)
+	}
+	if remaining := time.Until(expiry); remaining > 73*time.Hour || remaining < 71*time.Hour {
+		t.Errorf("expiry is %s away, want roughly 72h", remaining)
 	}
 }