docs: prepare the real landing page screenshot

[Periicles]

Prep work, not a finished change: everything is in place except the screenshot itself, which needs a machine with Screen Recording permission — mine does not have it.

Safe to merge as-is. With docs/assets/hero.png absent the page renders exactly as it does today, and it lights up the moment the file lands.

The capture script

scripts/capture-hero.sh reads the crop region from the panel's real window via CGWindowList rather than from a constant, so it cannot drift from ScreenHelper. It adds a margin either side so the notch reads as a notch rather than as a floating black box.

Two modes, because screencapture -R needs Screen Recording permission a terminal does not have by default — you hit that exact failure yourself:

scripts/capture-hero.sh                          # direct, needs the permission
scripts/capture-hero.sh --from ~/Desktop/x.png   # crops a Cmd-Shift-5 shot, needs nothing

The --from path derives pixels-per-point from the screenshot's own width instead of assuming the backing scale, so it is right whatever display it was taken on.

The page

The <img> ships hidden and is revealed by main.js only once it has actually loaded. A missing file therefore costs nothing — no broken image, no layout hole — and the CSS mockup stays as the fallback, including with JavaScript off. That is why this is mergeable before the asset exists.

Verification

• Ran the --from path end to end on an existing full-screen shot: region computed as 780×183pt at (510,0), cropped to 1560×366px at exactly 2×. The output was not committed — it showed your calendar names and the settings menu, which is precisely the kind of thing not to publish.
• Rendered the page offscreen with the asset absent: mockup shows, no broken image.
• Not verified: the reveal path in a real browser, since I have no browser here. The logic is a load listener plus a complete && naturalWidth check for the cached case.
• 28 i18n keys resolve both ways, node --check passes, bash -n on the script passes.

What is left for you

Run NotchBar during an actual event so the panel shows the in-progress state — title, times, progress bar. A shot of "No event today" would sell nothing. Then run the script, check the menu bar and event title in the frame are things you want public, and commit docs/assets/hero.png.