Venture loop: launch products, not pages

Ported from the notplanned venture template:
- launch round: every board seat writes a launch plan (positioning, first
  users, pricing, channels, 7-day success and kill lines); one seat
  synthesizes them into LAUNCH.md with where each idea came from
- launch page brief: one primary call to action in the hero, the working
  product preloaded with a sample, why-this-exists with real star counts,
  pricing (free plus at most two honest early-access tiers), honest limits,
  a design direction that rotates and never repeats the last six
- signups through a GitHub issue form prefilled with venture and plan;
  each signup is thanked on its own issue
- checks: deterministic gates, then headless Chrome measuring at exactly
  390x844 and 1280x800 (horizontal scroll, button below the fold, JS
  errors); two fix rounds, then andon with needs-human and /time retry
- a contact-sheet screenshot of phone and desktop on the card
- 7-day decision on distinct people: v2 card, kill, or one more week then
  park; a next version counts only signups after its own launch
- scheduling: a card that is measuring never blocks the others; one new
  card a day; a tick runs light stages back to back and one worker run
- the studio index at /ventures/ is generated from ventures.json

Security: the worker's shell no longer sees tokens or keys, its checkout
keeps no token in .git/config, and workflows don't persist credentials.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UpT7eWzeLhRwuYmsSQnbRb

.github/workflows/heartbeat.yml

@@ -34,6 +34,7 @@ jobs:
       - uses: actions/checkout@v5
         with:
           sparse-checkout: .github/time
+          persist-credentials: false   # the worker's shell must not find the token in .git/config
       - run: python3 .github/time/time.py heartbeat
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
@@ -51,3 +52,4 @@ jobs:
           TIME_PLANNER: ${{ vars.TIME_PLANNER }}
           TIME_WORKER: ${{ vars.TIME_WORKER }}
           TIME_WORKER_STEPS: ${{ vars.TIME_WORKER_STEPS }}
+          TIME_WORKER_MAX_TOKENS: ${{ vars.TIME_WORKER_MAX_TOKENS }}