staticcheck: the four items of the audit (stage 0)

- handlers/authz.go: domainIDSet removed, nothing called it (U1000).
- handlers_outbound_pages_test.go: two refusals whose status code was
  assigned and never read (SA4006) now check it is 400 - a custom DMARC
  report mode without an address, export passwords that differ.
- view/pages_test.go: !strings.Contains for a missing box (S1003).
- Audit plan line ticked, roadmap 6/61. No CHANGELOG line: nothing an
  operator sees changes.

staticcheck ./... clean afterwards. Evidence on the test server: see the
previous commit (same tree run).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/audit-2026-10-12.md

@@ -562,7 +562,7 @@ has already run is never edited — the next file is added; the published
 - [x] **Toolchain and deps**: `modernc.org/sqlite`, `x/crypto`, `x/sys`; note in
    development.md that the image is rebuilt after each Go patch release
    (`golang:1.26-bookworm` floats, so a rebuild suffices). — **Haiku**
-- [ ] The four `staticcheck` items. — **Haiku**
+- [x] The four `staticcheck` items. — **Haiku**
 - [ ] **A negative e2e case passes only on the refusal it is about** (owner,
    2026-10-14; seen, not found by the audit). `negative_level1_ratelimit`
    sends up to sixty messages and waits for one to be refused; it once

docs/roadmap.md

@@ -42,7 +42,7 @@ in `git log` and [CHANGELOG.md](../CHANGELOG.md).
 | from-header-binding | Hold a message's `From:` header against the application that sends it | shipped `2.4.0` | 9/9 | [plans/from-header-binding.md](plans/from-header-binding.md) |
 | panel-redesign | Panel redesign (accepted mockups, design contract) | shipped `2.0.0` | 27/27 | [plans/panel-redesign.md](plans/panel-redesign.md) |
 | schema-squash | Squash SQLite migrations into a 2.x baseline | built in panel-redesign (stage 1) | — | [plans/panel-redesign.md](plans/panel-redesign.md) |
-| audit-2026-10-12 | Follow-ups of the 2026-10-12 full-tree code audit, seven stages | agreed (2026-10-12: stage 0 first, then 1+2; the rest after) | 5/61 | [audit-2026-10-12.md](audit-2026-10-12.md) |
+| audit-2026-10-12 | Follow-ups of the 2026-10-12 full-tree code audit, seven stages | agreed (2026-10-12: stage 0 first, then 1+2; the rest after) | 6/61 | [audit-2026-10-12.md](audit-2026-10-12.md) |
 
 **Recommended order** (not binding; owner, 2026-10-09: feature order follows
 development convenience): **panel-redesign** shipped as `2.0.0` (2026-10-11) and

internal/web/handlers/authz.go

@@ -57,16 +57,3 @@ func domainNameSet(domains []store.Domain) map[string]bool {
 	}
 	return m
 }
-
-// domainIDSet is the set of sending domains a principal is limited to; nil
-// means no limit (the global role, or a domain user with All).
-func domainIDSet(p auth.Principal) map[int64]bool {
-	if p.IsGlobal() || p.AllDomains {
-		return nil
-	}
-	m := make(map[int64]bool, len(p.Domains))
-	for _, id := range p.Domains {
-		m[id] = true
-	}
-	return m
-}

internal/web/handlers/handlers_outbound_pages_test.go

@@ -172,6 +172,9 @@ func TestDomainSettingsRefusalsStayOnTheSettingsPage(t *testing.T) {
 	lacks(t, "report address refusal", body, `<b>`)
 
 	code, body = post(s.h.HandleDomainDMARC, "reports", url.Values{"dmarc_rua_mode": {"custom"}})
+	if code != http.StatusBadRequest {
+		t.Fatalf("a custom mode without an address = %d", code)
+	}
 	has(t, "report address refusal", body, `Enter the report address or choose another option.`)
 
 	code, body = post(s.h.HandleDomainDMARC, "reports", url.Values{"dmarc_rua_mode": {"hosted"}})
@@ -192,6 +195,9 @@ func TestDomainSettingsRefusalsStayOnTheSettingsPage(t *testing.T) {
 	}
 	has(t, "export refusal", body, `The encryption password must be at least 12 characters.`, `<h1 class="title is-3">Domain settings</h1>`)
 	code, body = post(s.h.HandleExportDomain, "export", url.Values{"encrypt": {"1"}, "password": {"long-enough-password"}, "password_confirm": {"another-one-entirely"}})
+	if code != http.StatusBadRequest {
+		t.Fatalf("export passwords that differ = %d", code)
+	}
 	has(t, "export refusal", body, `The two passwords do not match.`)
 }
 

internal/web/view/pages_test.go

@@ -167,7 +167,7 @@ func TestHealthShowsEveryCheckAndBothActions(t *testing.T) {
 	order := []string{`id="processes"`, `id="sender-check"`, `id="hostname"`, `id="machine"`,
 		`id="sockets"`, `id="certificate"`, `id="notification-mail"`, `id="configuration"`}
 	for i := 1; i < len(order); i++ {
-		if strings.Index(out, order[i-1]) < 0 || strings.Index(out, order[i]) < strings.Index(out, order[i-1]) {
+		if !strings.Contains(out, order[i-1]) || strings.Index(out, order[i]) < strings.Index(out, order[i-1]) {
 			t.Errorf("%s does not come after %s", order[i], order[i-1])
 		}
 	}