changelog: say why oldest-first matters (also moves the head past a status from a cancelled heartbeat run)

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017K4vyY3yUD3GsvoZaAtKkD

CHANGELOG.md

@@ -21,7 +21,7 @@
 - Seats review as themselves: with a `TIME_SEAT_<SEAT>` token (one Gitea user per seat, e.g. `TIME_SEAT_KIMI`) the reviewer's verdict is a real Gitea review by that user (Approve → approved, Object → changes requested, prose → comment), so reviews carry an identity and can count. Without a token, or if Gitea refuses (a seat on its own PR), it is Time's comment as before.
 - Cards can live on another branch. A `Base: <branch>` line in a card (`Base: gh-pages` for a venture) makes the seat worker cut its branch from that base, name it `time/card-N-<base>`, see that branch's files, and open the PR against it; without the line nothing changes. Until now every worker branched from the default branch whatever the card said, which is why the cards on `gh-pages` ran out of turns or opened PRs against `main`.
 - A launched worker finishes what it starts. The daily spend cap gates launches; a run that began within budget may go on to `TIME_CAP_SLACK` x the cap (default 1.5), and a PR that is already open gets its review on a capped day too. A run stopped mid-way had cost its whole spend and produced nothing. The monthly cap stays hard everywhere; `TIME_CAP_SLACK=1` restores the old stop.
-- The tick takes the oldest `ready` card first, the order `promote_next` already uses, instead of the newest the API lists first.
+- The tick takes the oldest `ready` card first, the order `promote_next` already uses, instead of the newest the API lists first, so a card promoted first is built first.
 - `TIME_PROTECTED` now governs every protected path except the workflow directories (`.github/workflows/`, `.gitea/workflows/`), which stay a human's merge whatever it says. The default still protects all of `.github/`; a repo that trusts its reviewer can set `TIME_PROTECTED=.github/workflows/,.gitea/workflows/,deploy,infra/,.env,secret` so the engine under `.github/time/` merges itself on Approve + green like any other code.
 - Objections go back to the worker. `/time retry` on a card whose PR is open hands the worker the reviewer's latest comments (marked as the reviewer's, strangers' left out) on the same branch; `open_pr` on an open PR updates its description instead of failing; the card goes back to `dispatched`, so the next beat reviews again and an objection older than the push no longer counts.
 - A batch's children start in the tick that spawned them (GitHub lists a card made a moment ago only later, so they used to wait a tick).