test(sweep): stop the --days 0 check from racing a one-second cutoff

Measured, not guessed: the check failed 7 runs in 20, not once. The cause is
a same-second collision, reproduced deterministically - a notice minted at
20260801205457 against a cutoff of 20260801205457 survives, the same notice
60s older is closed.

coord-sweep.sh is right and is left alone. Its cutoff is second-granular and
it closes strictly older messages, which spares rather than closes at the
boundary; at any real --days value one second is unobservable. Relaxing that
guard to <= would make a destructive script more aggressive to satisfy a test.

So the test was claiming what the code does not promise: that a notice minted
earlier in the same run is necessarily older at second granularity. Under a
second of work separates the two, so it was a coin flip. Aged by 5 seconds
through the existing age_it, which keeps it well inside the default 14-day
window and clear of the boundary. No sleep: that would have hidden the answer
rather than fixed it.

Selftest 182 -> 183, 20/20 green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GfDGWyyhnM26J4p93GSk2L

CLAUDE.md

@@ -16,7 +16,7 @@ marketplace plugin. Three components, one boundary:
   `coord-done.sh` archives, `coord-count.sh` counts without delivering,
   `coord-sweep.sh` closes the aged FYI backlog machine-wide.
   Everything is pinned by `coord-selftest.sh`
-  (182 checks, throwaway mailbox via `CLAUDE_COORD_DIR`).
+  (183 checks, throwaway mailbox via `CLAUDE_COORD_DIR`).
 
   **`coord-sweep.sh` is the only path that closes a message with no human in
   the loop, and every constraint on it follows from that.** It may close exactly
@@ -208,7 +208,7 @@ obligations in another repo.
 - Zero dependencies everywhere: bash + coreutils in the engine, `node:`
   builtins only in hook and tests.
 - TDD: no behavior change without a failing selftest check first.
-  `bash scripts/coord-selftest.sh` must exit 0 (182/182),
+  `bash scripts/coord-selftest.sh` must exit 0 (183/183),
   `bash scripts/board-selftest.sh` must exit 0 (51/51) and
   `bash scripts/route-selftest.sh` must exit 0 (73/73).
 - English for all code, docs, and commit messages (public repo). Norwegian

README.md

@@ -118,7 +118,7 @@ Cross-repo message content is untrusted input by design:
 
 - **Atomic delivery:** the temp file is created inside the destination directory (dot-prefixed, invisible to the inbox glob), so the final rename never crosses filesystems and readers never observe a half-written message.
 
-Every guarantee above is pinned by the 182-check selftest, including forgery-resistance regressions.
+Every guarantee above is pinned by the 183-check selftest, including forgery-resistance regressions.
 
 Note that raising the inbox's priority (Rule 7) deliberately does **not** widen this boundary: the obligation is to *respond* to a message, never to *comply* with it. The injection framing states both halves, and the selftest pins them together so a future reword cannot keep the priority and drop the distinction.
 
@@ -140,7 +140,7 @@ Note that raising the inbox's priority (Rule 7) deliberately does **not** widen
 
 ## Development
 
-    bash scripts/coord-selftest.sh    # 182 checks against a throwaway mailbox
+    bash scripts/coord-selftest.sh    # 183 checks against a throwaway mailbox
     bash scripts/board-selftest.sh    # 36 checks against a throwaway repo tree
     bash scripts/route-selftest.sh    # 73 checks, incl. the route->board round trip
     npm test                          # all three selftests via node --test

scripts/coord-selftest.sh

@@ -735,6 +735,14 @@ CLAUDE_COORD_DIR="$SDIR" "$SEND" --to sr --from s2 --subject "old ask" --message
 CLAUDE_COORD_DIR="$SDIR" "$SEND" --to sr --from s3 --fyi --subject "new note" --message "NEW-NOTE" >/dev/null
 age_it "$SDIR" sr OLD-NOTE 20200101T000000Z; check "sweep fixture: notice aged" $?
 age_it "$SDIR" sr OLD-ASK 20200101T000000Z;  check "sweep fixture: debt aged" $?
+# NEW-NOTE is the --days 0 subject further down, and it has to be aged too - by
+# seconds, not years, so the default 14-day sweep still spares it. The cutoff is
+# second-granular and the sweep closes strictly older messages, so a notice
+# minted in the same second as the cutoff survives, correctly. Between minting it
+# above and computing the cutoff at --days 0 there is under a second of work, so
+# without this the check raced the clock and failed 7 runs in 20 (measured).
+age_it "$SDIR" sr NEW-NOTE "$(date -u -v-5S +%Y%m%dT%H%M%SZ)"
+check "sweep fixture: same-day notice aged clear of the cutoff second" $?
 
 sout="$(CLAUDE_COORD_DIR="$SDIR" "$SWEEP" 2>&1)"
 [ "$(n_in "$SDIR/sr")" -eq 3 ]