Localhost port watcher: detects a newly bound dev-server port via
bounded TCP probing, opens an iframe preview pane, and captures a
one-click timestamped screenshot receipt via headless Chrome. No
Claude Code changes, stdlib-only, 16 passing tests plus a real
end-to-end dogfood (demo.py) with a genuine recorded screenshot.
Landing page at ventures/preview-sidecar/site/index.html uses a
receipt/ticket visual identity (narrow thermal-paper column, dotted
rules, wax stamp, monospace totals) distinct from the finishline
venture, with one above-the-fold signup CTA and an honest free/paid
pricing section.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
