venture batches: the board's top k as one milestone, launched together (multi-ceremony) (#22)

One batch card scouts once, the seats pitch a field, and the board ranks it; the top k
(each wanted by two seats) become venture cards in the batch's milestone at 'picked'.
Children run the ordinary loop side by side, wait at 'ready' until every sibling is
settled or the hold runs out, then launch together. No child left behind: one batch
retry for a held child, then it is counted dead in the cohort retro, which closes the
card and the milestone. Fix rounds now yield the single worker run per tick to cards
still due their first build, so a failing page can't starve its siblings.


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

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

.github/workflows/venture.yml

@@ -2,6 +2,7 @@ name: venture
 # The venture loop: trending repos -> pitches -> board -> launch plan -> launch page on Pages -> 7 days of signups.
 # Every 20 minutes it advances whatever is due (cheap when nothing is); a new venture card starts once a day,
 # or right away: Actions -> venture -> Run workflow -> tick "Start a new venture now" (gh workflow run venture.yml -f start=true).
+# Batches: TIME_VENTURE_BATCH=3 (or Run workflow -> batch) runs k ventures at once in one milestone.
 # Off until TIME_VENTURE=on. Signups come in through .github/ISSUE_TEMPLATE/early-access.yml.
 on:
   schedule:
@@ -12,6 +13,10 @@ on:
         description: "Start a new venture now, even if today's has already run"
         type: boolean
         default: false
+      batch:
+        description: "Start a venture batch now: one scout, the board's top k, launched together (k = TIME_VENTURE_BATCH, or 3)"
+        type: boolean
+        default: false
 permissions:
   contents: write
   issues: write
@@ -39,6 +44,9 @@ jobs:
           TIME_VENTURE_AI_MODEL: ${{ vars.TIME_VENTURE_AI_MODEL }}
           TIME_VENTURE: ${{ vars.TIME_VENTURE }}
           TIME_VENTURE_START: ${{ inputs.start && '1' || '' }}
+          TIME_VENTURE_BATCH_START: ${{ inputs.batch && '1' || '' }}
+          TIME_VENTURE_BATCH: ${{ vars.TIME_VENTURE_BATCH }}                    # k; set, a batch replaces the daily single card
+          TIME_VENTURE_BATCH_HOLD_HOURS: ${{ vars.TIME_VENTURE_BATCH_HOLD_HOURS }}  # launch-together hold (default 6)
           TIME_VENTURE_PITCH: ${{ vars.TIME_VENTURE_PITCH }}
           TIME_VENTURE_BOARD: ${{ vars.TIME_VENTURE_BOARD }}
           TIME_VENTURE_CHAIR: ${{ vars.TIME_VENTURE_CHAIR }}