venture: children start the tick they're spawned; briefs claim only what the code does (#33)

Two findings from the first live batch (#26):
- its children waited a tick: GitHub doesn't list a card made a moment ago. spawn()
  now hands its cards to the same tick's card loop.
- every fix round was a page claiming what its code didn't do: promised drops, and
  'builds on' the trending repos the brief asked it to name. The brief now says the
  repos are the wave it rides, forbids promised features, and has the worker re-read
  the page against app.js; fix rounds remove a failing claim instead of building.


Claude-Session: https://claude.ai/code/session_01VDkN7ukK1kXkqov8FaZxva

Co-authored-by: Claude <noreply@anthropic.com>

CHANGELOG.md

@@ -7,6 +7,8 @@
 - The Venice worker's shell no longer sees secrets: its environment drops tokens and keys, its checkout keeps no token in `.git/config`, and the workflows check out without persisted credentials.
 
 ### Added
+- 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).
+- Build briefs keep claims to what the code does: no promised features or schedules, and the trending repos are the wave a venture rides, never something it "builds on". Fix rounds take a failing claim off the page rather than building a feature in a hurry. In the first live batch, every fix round was a claim the code didn't back.
 - Venture batches (multi-ceremony): one batch card scouts once, the seats pitch a field (rounds until there are 2k pitches), and the board ranks the whole field; the top k, each wanted by two seats, become venture cards in the batch's own milestone. They run the ordinary loop side by side and launch together: a child that passes its checks waits at `ready` until every sibling is settled or the hold (`TIME_VENTURE_BATCH_HOLD_HOURS`, 6) runs out; stragglers then launch alone. No child left behind: a held child gets one batch retry, and held again it is counted dead with its reason. A retro on the batch card compares the cohort's signups against each plan's lines, then the card and milestone close. Set `TIME_VENTURE_BATCH=3` to make batches the daily default, or Actions → venture → Run workflow → "batch".
 - Parallel builds: a tick runs up to `TIME_VENTURE_HEAVY` (default 3) worker runs at once, one per card, so a batch builds in one tick instead of three. Each build keeps its own folder lock, `ventures.json` is updated under a lock with a fresh read, and a Pages write that loses the race for the branch head (409) is retried. `TIME_VENTURE_HEAVY=1` is the old one-at-a-time.
 - Fix rounds yield the worker runs to cards still due their first build, so a page that keeps failing can't starve the others.