Pins a late event before and after the reap

[johnnyt]

Pins what a late event meets once its execution has finished, before and after StatifierRouter.Addresses.reap/3 deletes the execution's address row, under each create mode, and records the trade as the host's. Nothing under lib/ changes.

Bead: sr-n0y4.

What changes

• Tests. StatifierRouter.LatePartnerTest (test/statifier_router/late_partner_test.exs), over the parcel chart and the parcel scan bindings already in the test support:
  • :if_absent: a late delivered scan is dropped: finished before the reap, and after the reap it opens a second execution for the parcel;
  • :if_absent: the longest dedupe horizon of any enabled binding naming the document is what keeps the row, and a disabled binding's longer horizon does not count;
  • :never: the late scan is dropped: finished before the reap and dropped: no_execution after it, creating nothing;
  • :never: its cost, a delivered scan that arrives before its loaded scan is lost;
  • :always_new: every scan opens its own execution before and after a reap, which finds no row.
• Record. A dated Note at the foot of docs/adr/0002-addressing.md: the knob is the dedupe horizon, a document no enabled binding names (one reached only through the execution target) has a horizon of zero, a per-mode table of what a late event meets, and create: :never on the partner binding as the first-line answer with its cost. A refusing create mode and a tombstone kept past the address row are left for a later record.
• README. One paragraph in "The host schedules the reapers", after the Addresses.reap/2 paragraph, naming the same knob and trade.

No changelog fragment: tests and docs only, which changelog.d/README.md excludes.

Provenance

The trade documented as the host's, with no new create mode and no tombstone in this change: ruled by the operator, 2026-10-01.

Direction check of the Note

Every claim was read against main at the branch's base. The horizon is the longest horizon_ms of the enabled bindings naming the document, read per call (the private horizons/1 of StatifierRouter.Addresses, reached through reap/3), and counted from terminal_seen_at (ADR-0002, sections 5 and 6; the private due?/3). A dedupe row's expires_at is the delivery's time plus the same horizon_ms (StatifierRouter.Dedupe.claim/4). The per-mode table matches ADR-0003, section 4 and the private by_mode/4 and absent/4 of StatifierRouter.Delivery; the "after" column of if_absent is the created path's outcome, created_and_delivered or dropped: unmatched_event (ADR-0004), and the test shows the second for a scan the chart's first state does not take. always_new writing no row is ADR-0002, section 7. The Note opens with the house sentence, cites by anchor, and the diff removes zero lines under docs/adr/.

Verification

• Full mix quality green on the committed tree: the isolated stage, the suite, Dialyzer, Docs and Doc links.
• The kit's pre-request review round ran on the branch (a diff critic and a test critic); its accepted findings are in this commit: the if_absent after-reap cell names both outcomes, the Note says terminal_seen_at is never earlier than the finish, the knob test orders the longest horizon first and carries a disabled binding, and the Note's tests bullet says exactly what is pinned.
• Each new test was sabotaged against the lib/ lines it covers and went red on an assertion; the mutation is noted above each test.