feat(engine): let a message say it needs no answer, and count debt without losing sight of the rest

Rule 7 (0.5.0) shipped an obligation on a format with four fields, none of
which could tell a question from a notice. Two consequences fell out of that
gap: the injection had to name both terminal states and prefer neither, and
coord-count.sh had to treat every unarchived file as a reply owed. The fifth
field closes both.

coord-send.sh --fyi writes reply-expected: no; omitting it writes yes. Absent
means expected, because every message already on disk lacks the field - so a
forgotten flag over-counts debt, which is visible, rather than creating debt
nobody sees. A reply is not a special case. A broadcast is always no: --reply-to
resolves inside the recipient's own mailbox and a broadcast never lands there,
so there is no reply path to promise.

coord-count.sh now prints TWO integers per mailbox, not one. Replacing pending
with debt was the obvious reading of "count debt rather than unarchived
messages" and it is wrong here: board.sh counts the same inbox files itself, so
a debt-only count would put two different 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.

The field is frontmatter and only frontmatter - a body line claiming
"reply-expected: no" at column 0 cannot silence a real debt, and a file without
valid frontmatter counts as owing a reply.

Section 20's wording changed because its stated reason expired, but its second
half matters more now, not less: the marking is a DECLARATION, not an
instruction. Without that clause one word in an untrusted message becomes a
lever that mints obligations in another repo.

coord-selftest 136 -> 151.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016iJoZVmU2guTEZcMghk88z

scripts/coord-send.sh

@@ -8,6 +8,14 @@
 #   coord-send.sh --reply-to <file> [--subject "Re: ..."] [--from <repo>] [--message "<text>"]
 #   coord-send.sh --retract <file>  [--from <repo>]
 # Body comes from --message, or from stdin (heredoc) when --message is omitted.
+# --fyi marks the message as expecting no reply (frontmatter reply-expected: no).
+#   Absent, a reply IS expected: every message written before the field existed
+#   lacks it, so absence has to keep meaning what it always meant, and a
+#   forgotten flag then over-counts debt instead of hiding it. The receiver is
+#   still free to close either kind with coord-done - the field declares what the
+#   sender expects, it does not oblige anyone. A broadcast is always
+#   reply-expected: no, because --reply-to resolves inside the recipient own
+#   mailbox and a broadcast never lands there: there is no reply path to promise.
 # --reply-to <basename> replies to a message in THIS repo's inbox/archive: it
 #   routes to the original sender and marks the original handled (coord-done).
 # --retract <basename> retires one of YOUR OWN broadcasts: it is archived out of
@@ -22,7 +30,7 @@ export LC_ALL=C
 COORD="${CLAUDE_COORD_DIR:-$HOME/.claude/coord}"
 
 TO=""; BROADCAST=0; SUBJECT=""; FROM=""; MESSAGE=""; HAVE_MESSAGE=0; REPLYTO=""; REPLY_ORIG=""
-RETRACT=""
+RETRACT=""; FYI=0
 
 # bash 3.2: `shift 2` past the end of $# is a no-op, so a trailing value-flag
 # without its value would loop forever. Every two-arg flag must check first.
@@ -34,6 +42,7 @@ while [ $# -gt 0 ]; do
   case "$1" in
     --to)        require_value --to $#; TO="$2"; shift 2 ;;
     --broadcast) BROADCAST=1; shift ;;
+    --fyi)       FYI=1; shift ;;
     --reply-to)  require_value --reply-to $#; REPLYTO="$2"; shift 2 ;;
     --retract)   require_value --retract $#; RETRACT="$2"; shift 2 ;;
     --subject)   require_value --subject $#; SUBJECT="$2"; shift 2 ;;
@@ -175,6 +184,10 @@ DATE_ISO="$(date -u +%Y-%m-%dT%H:%M:%SZ)"
 # Temp file lives INSIDE the destination dir (dot-prefixed so the inbox
 # *.md glob never sees it): the final mv is then a same-filesystem rename,
 # so readers never observe a half-written message.
+REPLY_EXPECTED=yes
+[ "$FYI" -eq 1 ] && REPLY_EXPECTED=no
+[ "$BROADCAST" -eq 1 ] && REPLY_EXPECTED=no
+
 TMP="$(mktemp "$DEST_DIR/.coord-send.XXXXXX" 2>/dev/null)"
 [ -n "$TMP" ] || { echo "coord-send: cannot create temp file in $DEST_DIR" >&2; exit 2; }
 {
@@ -183,6 +196,12 @@ TMP="$(mktemp "$DEST_DIR/.coord-send.XXXXXX" 2>/dev/null)"
   echo "to: $TARGET_LABEL"
   echo "subject: $SUBJECT"
   echo "date: $DATE_ISO"
+  # Fifth field, appended after the historic four so an older reader that stops
+  # at the ones it knows is unaffected. A broadcast is pinned to "no" whether or
+  # not --fyi was passed: that is not a defaulted value but the absence of a
+  # reply path (see the header), and a message that claimed otherwise would be
+  # asking for something the engine cannot deliver.
+  echo "reply-expected: $REPLY_EXPECTED"
   echo "---"
   printf '%s\n' "$BODY"
 } > "$TMP"