feat(coord,board): flag mailboxes no session has ever read (WP1d detection half)

coord-count.sh gains a fourth TSV column: "-" when a mailbox has .origin
(a real session has read it via SessionStart), otherwise the age in whole
days of the oldest pending message. .origin is only written by
coord-inbox.sh's non---repo path, so its absence means the mailbox is
never reached by normal injection — a genuine dead letter, not merely
slow. board.sh's --brief surfaces mailboxes past the 3-day threshold as
a new "ALDRI LEST" section, mirroring the existing orphan-mailbox
listing. This is WP1d's detection half only (per .claude's coord
bestilling 2026-08-14); the action half (report-to-sender / retract) is
unapproved design, not built here.

coord-selftest.sh: 191 -> 197 checks. board-selftest.sh: 175 -> 178
checks (net +3; section 16 adds 3 new fixtures on top of the existing
175 baseline, some pre-existing counts shift with the trailing column).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0194eV8b6BXNv6aKLovP8TP6

scripts/coord-count.sh

@@ -1,7 +1,8 @@
 #!/bin/bash
 # coord-count.sh - count PENDING directed messages per mailbox WITHOUT
-# delivering anything. Prints one "<mailbox>\t<pending>\t<debt>" line per mailbox
-# that has unhandled mail, sorted by name; prints nothing when none do.
+# delivering anything. Prints one "<mailbox>\t<pending>\t<debt>\t<origin_age>"
+# line per mailbox that has unhandled mail, sorted by name; prints nothing when
+# none do.
 #
 # TWO INTEGERS, NOT ONE. <pending> is every unhandled message; <debt> is the
 # subset whose sender declared it expects a reply (frontmatter reply-expected,
@@ -11,6 +12,15 @@
 # numbers under one name with nothing to reconcile them - and a mailbox holding
 # only notices would read as empty while its messages keep being re-injected.
 #
+# <origin_age> (WP1d, .claude 2026-08-14): "-" when the mailbox has a .origin
+# file, otherwise the age in whole days of its OLDEST pending message.
+# coord-inbox.sh writes .origin only from a REAL session's own SessionStart
+# (REPO_PATH resolved via git rev-parse, never when --repo is passed
+# explicitly), so a mailbox with no .origin has NEVER been reached by the
+# normal per-repo injection - pending mail there is a dead letter, not merely
+# slow. This script only reports the raw age; judging it against a threshold
+# is board.sh's job, the same split as <pending> vs <debt> above.
+#
 # WHY THIS IS NOT coord-inbox.sh --repo <x>: reading IS delivery. The read path
 # prints a broadcast and then records it as seen, so asking it "what is pending
 # for x" would consume x's broadcast backlog as a side effect - once, silently,
@@ -78,18 +88,46 @@ for d in "$COORD"/* "$COORD"/.[!.]*; do
   [ -d "$d/inbox" ] || continue
   # *.md is the message grammar; a stray file must not inflate a total the
   # operator reads as "replies owed".
-  n=0; owed=0
+  # oldest_ts captures only the FIRST message whose filename matches the
+  # timestamp grammar. That is safe because the glob above is already
+  # name-sorted under LC_ALL=C (see the comment on it), and the grammar's
+  # timestamp prefix sorts identically to chronological order - so the first
+  # match encountered is the oldest, without a second pass or a full sort.
+  n=0; owed=0; oldest_ts=""
   for m in "$d/inbox"/*.md; do
     [ -e "$m" ] || continue
     n=$((n + 1))
     owes_reply "$m" && owed=$((owed + 1))
+    if [ -z "$oldest_ts" ]; then
+      mts="${m##*/}"
+      mts="${mts%%-*}"
+      case "$mts" in
+        [0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]T[0-9][0-9][0-9][0-9][0-9][0-9]Z)
+          oldest_ts="$mts" ;;
+      esac
+    fi
   done
   [ "$n" -gt 0 ] || continue
+  # "-" means either .origin exists (claimed, never a dead-letter candidate
+  # regardless of age) or the age could not be read (fail-safe, not
+  # fail-open - an unreadable age must never be treated as old, matching
+  # coord-sweep.sh's identical rule for the same filename grammar).
+  origin_age="-"
+  if [ ! -f "$d/.origin" ] && [ -n "$oldest_ts" ]; then
+    oldest_epoch="$(date -u -j -f '%Y%m%dT%H%M%SZ' "$oldest_ts" '+%s' 2>/dev/null)"
+    case "$oldest_epoch" in
+      [0-9]*)
+        now_epoch="$(date -u +%s)"
+        age_days=$(( (now_epoch - oldest_epoch) / 86400 ))
+        [ "$age_days" -ge 0 ] && origin_age="$age_days"
+        ;;
+    esac
+  fi
   # Absent, not zero: the question is "who has unhandled mail", and a list of
   # zeroes answers a different one at every reader's expense. A mailbox holding
   # only notices IS listed, with a debt of 0 - it has mail that will be
   # re-injected until someone closes it, which is the thing worth knowing.
-  printf '%s\t%s\t%s\n' "$name" "$n" "$owed"
+  printf '%s\t%s\t%s\t%s\n' "$name" "$n" "$owed" "$origin_age"
 done
 
 exit 0