audit 6: documents, comments, dead code and staticcheck; the test gaps closed

The last stage of the 2026-10-12 audit; no cut.

Doc drift: architecture.md (the sender check in § OpenDKIM, the limit:
row's 48 hours, the inbound log and filter-list routes and who may open
them, migrations to 0011 and every table, KitPage as production data,
Reload configuration as a restore writes, the panel's roles counted),
schema-migrations.md (tables and columns since v2), guide.md (a delivery's
lines go at the next prune; INBOUND_JOURNAL_MILTER_SOCKET moved to
architecture.md's internal list), development.md (the env guard, the
deferral the e2e proves, its fixed sleeps), roadmap.md.

Comments say what the code does now; TestBaselineIsTheOnlyMigration is
TestChainStartsAtTheBaseline; the milter package doc names its three
milters.

Dead code gone: view.Facts, dmarc HostedSuggestion and
ValidateHostedAddress, app UpdateMode (each with the test that alone kept
it), the method checks the method-bound routes made dead;
Settings.WithResult calls resultFlash. staticcheck 2026.1 in test.yml on
both modules, clean: the e2e package builds without its tests now (a test
and two constants moved out of non-test files), three findings fixed.
The test moved, TestImageBuildPreservesLogrotateMode, had sat in a
non-test file and never run; run, it failed on the entrypoint (docker run
without a hostname) and now asks with --entrypoint stat.

The test gaps no step named, each closed: follow() with mail.log gone past
blindMin and made again; CheckRestore with a manifest that is not JSON;
the origin check with a port; every /server/ pattern in web.go through
server() and in the routes table (it found GET /server/health/fragment
missing from the table - guarded, not tested); L9 as the owner decided it
on 2026-10-12, the comment on senderSession.Headers and the test passing
an h that holds the earlier messages' From:.

Plan stage 6 ticked; roadmap audit row done, 81/81.

Tested on the test server: go vet + go test of 27 packages, make e2e (all
pass, 513 s) on this tree; staticcheck locally on both modules.

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

internal/web/handlers/handlers_settings.go

@@ -25,15 +25,12 @@ func (h *Handlers) HandleServerSettings(w http.ResponseWriter, r *http.Request)
 	if _, ok := h.requireGlobal(w, r); !ok {
 		return
 	}
-	switch r.Method {
-	case http.MethodGet:
-		h.renderServerSettings(w, r, http.StatusOK, "", h.currentRetentions())
-	case http.MethodPost:
+	// The routes are method-bound (GET and POST), so it is one or the other.
+	if r.Method == http.MethodPost {
 		h.submitServerSettings(w, r)
-	default:
-		w.Header().Set("Allow", "GET, POST")
-		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
 	}
+	h.renderServerSettings(w, r, http.StatusOK, "", h.currentRetentions())
 }
 
 // retentions are the two journal retentions the Settings form shows: the