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/milter/sender.go

@@ -328,6 +328,11 @@ func (s *senderSession) Header(name, value string, m *milter.Modifier) (milter.R
 // src/cleanup/cleanup_milter.c, cleanup_milter_apply(): a "5" rejects the
 // message, and src/smtpd/smtpd.c, common_post_message_handling(), says that
 // reply to the client.
+//
+// h is not read: go-milter v0.4.1 adds every header of the connection to it
+// and empties it only on ABORT (session.go, CodeHeader, CodeAbort), so on a
+// second message it can still hold the first one's From:. The session keeps
+// its own, emptied at each MAIL FROM (audit 2026-10-12, L9).
 func (s *senderSession) Headers(h textproto.MIMEHeader, m *milter.Modifier) (milter.Response, error) {
 	shown, why, err := s.judge()
 	if err != nil {