Describe code in its own terms, not by an earlier build's data (closes #522)

Several comments justified code by what an earlier build would have
left in a database or on disk. Each now says what the code does:
reserveSQLiteFile sets the mode on every open whoever created the
file, and expired treats a session lacking a deadline's timestamp as
expired. The comments on retention, resubmitted events, archive
pruning, target headers, the redactor and the delivery result view
drop their mentions of older rows. Comments only.

Model: opus-5-5

internal/database/model_event.go

@@ -45,8 +45,7 @@ type Event struct {
 
 	// ResubmittedFromID names the event this one was copied from by
 	// an operator resubmit. It is nil for an event that arrived on
-	// the receiver, which is every event created before the column
-	// existed. It is not a foreign key: the source event can be
+	// the receiver. It is not a foreign key: the source event can be
 	// reaped by retention while its copies remain, and the id is
 	// kept as the record of where the copy came from either way.
 	ResubmittedFromID *string `gorm:"type:uuid;index:idx_events_resubmitted_from_id,priority:1;index:idx_events_entrypoint_id,priority:3" json:"resubmittedFromId,omitempty"`

internal/database/model_webhook.go

@@ -98,8 +98,8 @@ func (w *Webhook) BeforeSave(_ *gorm.DB) error {
 // are exempt from reaping.
 //
 // It accepts the RetentionForeverDays sentinel written by BeforeSave
-// and, defensively, the non-positive values that rows written before
-// the sentinel existed may still carry.
+// and, defensively, any non-positive value, which BeforeSave treats
+// as a request to retain forever.
 func retainsForever(retentionDays int) bool {
 	return retentionDays <= 0 ||
 		retentionDays >= RetentionForeverDays

internal/database/retention.go

@@ -253,7 +253,7 @@ func (r *RetentionReaper) reapWebhook(
 // row in the database: the sweep then deletes every event, delivery,
 // and delivery result, including ones created seconds ago. Rejecting
 // out-of-range input at the form is the primary guard; saturating here
-// means an old row, a migration, or a future call site cannot turn a
+// means a value that reaches the row by any other path cannot turn a
 // too-large retention into total data loss.
 func retentionCutoff(
 	now time.Time,

internal/database/sqlite_open.go

@@ -118,9 +118,8 @@ const SQLiteFilePerm fs.FileMode = 0o600
 // SQLite still reports the absence rather than this function
 // materializing an empty database the caller asked not to create.
 //
-// Chmod of a file that already exists is what tightens a data
-// directory an earlier build left at 0644 — including a developer's
-// own scratch directory — without any migration machinery.
+// The mode is set on every open, whoever created the file, so a
+// database or sidecar found at a wider mode is tightened too.
 func reserveSQLiteFile(path string, create bool) error {
 	if create {
 		// gosec G304: the path is the database file the caller asked

internal/delivery/archive_sweeper.go

@@ -201,8 +201,7 @@ func (s *ArchiveSweeper) sweep(ctx context.Context) {
 
 // sweepTarget prunes the archive of a single database target.
 // A missing, empty, or "never" expiry parses as a zero duration
-// and is skipped entirely, so those archives keep exactly the
-// behaviour they had before the sweep existed.
+// and is skipped entirely, so those archives are never pruned.
 func (s *ArchiveSweeper) sweepTarget(target *database.Target) {
 	expiry, err := parseArchiveExpiry(target.Config)
 	if err != nil {

internal/delivery/target_headers.go

@@ -82,8 +82,8 @@ func isReservedTargetHeader(name string) bool {
 // one pair silently overwriting the other.
 //
 // An input with no pairs yields an empty map, which omitempty drops
-// from the stored config: a target configured with no headers keeps
-// the same config JSON it had before this field existed.
+// from the stored config, so a target configured with no headers
+// stores no headers key at all.
 func ParseTargetHeaders(raw string) (map[string]string, error) {
 	headers := make(map[string]string)
 

internal/delivery/target_redact.go

@@ -13,9 +13,9 @@ import (
 const RedactionMarker = "(redacted)"
 
 // Redactor removes one target's own credential material from
-// text that target's remote peer chose: a delivery response
-// body, or a delivery error stored before the delivery path
-// learned to mask the URLs it embeds.
+// a delivery response body, whose text the target's remote
+// peer chose, and from a stored delivery error as a second
+// line behind the delivery path's own URL masking.
 //
 // It removes byte-identical echoes of strings taken from the
 // target's stored configuration, and nothing else. Anything

internal/handlers/delivery_result_view.go

@@ -12,13 +12,12 @@ import (
 //
 // The bound is enforced here and in SQL, because this page's
 // memory profile must not depend on a constant in another
-// package staying where it is, and because rows predating the
-// delivery engine's own cap or restored from an archive are
-// not covered by it at all.
+// package staying where it is, or on every stored row having
+// been written by the delivery engine under its own cap.
 //
 // It happens to equal that engine cap, so a row written by the
-// current engine reaches this one exactly and is never cut
-// twice. Nothing here may assume the two differ: see view.
+// engine reaches this one exactly and is never cut twice.
+// Nothing here may assume the two differ: see view.
 const maxRenderedResponseBytes = 4096
 
 // deliveryResultColumns is the delivery attempt projection.
@@ -40,9 +39,8 @@ const deliveryResultColumns = "delivery_id, attempt_num, created_at, " +
 //
 // Both Error and ResponseBody have been through the target's
 // Redactor. The engine already masks the URL out of the
-// errors it stores, so for errors this is a second line
-// covering rows written before it did; for response bodies it
-// is the only line, and its reach is what
+// errors it stores, so for errors this is a second line; for
+// response bodies it is the only line, and its reach is what
 // delivery.Redactor documents.
 type DeliveryResultView struct {
 	AttemptNum int

internal/session/session.go

@@ -441,10 +441,9 @@ func (s *Session) Regenerate(
 //
 // Whichever comes first ends the session.
 //
-// A session that claims to be authenticated but carries no
-// timestamps predates this check; it is treated as expired so the
-// user re-authenticates rather than being granted an unbounded
-// session.
+// A session that claims to be authenticated but lacks the timestamp
+// a deadline is measured from is treated as expired, so the user
+// re-authenticates rather than being granted an unbounded session.
 func (s *Session) expired(sess *sessions.Session) bool {
 	now := s.now()