Add Smart App Banner to share pages for post-install one-tap re-open

[variablefate]

Goal

Add Apple's Smart App Banner (<meta name="apple-itunes-app">) to each driver-share page so that a user who has RoadFlare installed and revisits roadflare.app/share/d/<npub> in iOS Safari sees a native "OPEN" banner that launches the app pre-filled with the driver. For users without the app, the same banner shows "VIEW" → App Store.

This is a one-<meta>-tag quick-win, complementary to the App Clip work that bridges the first-install gap. It does NOT replace App Clip.

Why this is its own issue

<meta name="apple-itunes-app"> only carries app-argument to an already-installed app. The argument is stripped by iOS during install. So this issue covers exactly one case: a returning user who already has RoadFlare and re-opens a share link in Safari. Common scenario — driver texts the share URL to a rider, rider taps once before installing (App Clip handles that — see variablefate/roadflare-ios#75), then later reopens the same link to add another driver.

Implementation

Single change to 404.html (the SPA router for /share/d/<npub> and /share/r/<npub>).

Inside renderSharePage(type, npub), after the npub is parsed and BEFORE any heavy rendering, inject the meta tag:

// Smart App Banner — drivers only; rider scheme has no handler yet.
if (isDriver) {
    const meta = document.createElement('meta');
    meta.name = 'apple-itunes-app';
    const realName = profile.display_name || profile.name || '';
    const nameParam = realName ? '?name=' + encodeURIComponent(realName) : '';
    meta.content = `app-id=6761305625, app-argument=roadflared:${npub}${nameParam}`;
    document.head.appendChild(meta);
}

(Skip on rider shares for now — roadflarer: has no iOS handler today; setting the meta there would surface an "OPEN" button that does nothing useful until a future driver app ships and registers the scheme.)

How this interacts with the rest of the deep-link surface

Three layers of share-link → app dispatch are converging:

Layer	Status	Pre-install?	Post-install?
Smart App Banner (this issue)	proposed	falls back to App Store via app-id	"OPEN" button passes roadflared:<npub> to running app
App Clip (variablefate/roadflare-ios#75)	proposed	downloads ~10 MB clip, previews driver, hands off via App Group on install	bypassed in favor of Universal Link
Universal Links (variablefate/roadflare-ios#63)	proposed	falls back to current share page	https://roadflare.app/share/d/<npub> opens app directly

The three are additive — same AASA on this site can host applinks (#63) and appclips (#75) sections side by side; this issue's meta tag is independent and lives in the rendered HTML, not AASA.

Limitations (intentionally accepted)

• Only Safari renders Smart App Banners. Chrome iOS does not — but Chrome iOS users tapping share links from Mail/Messages get routed through Safari anyway.
• app-argument is NOT preserved through install. App Clip (variablefate/roadflare-ios#75) is the answer for first-install context bridging.
• Some users dismiss the banner. iOS persists the dismissal per-domain. Not worth fighting.
• Banner shows above the existing share-page UI, briefly nudging the page down. Acceptable.

Prerequisites

• PR variablefate/roadflare-ios#66 merged + shipped to App Store. The banner's app-argument=roadflared:<npub> value relies on the iOS app's URL-scheme handler that #66 introduces. Until #66 is live in an App Store build, the banner would correctly route to the App Store install but tapping "OPEN" on an existing pre-#66 install would do nothing.
• Site PR can be opened ahead of time and held draft until #66 ships, similar to draft PRs #4 and #5.

Out of scope

• Rider share banner (no roadflarer: handler exists yet)
• AASA changes (handled by #63 / #75 on the iOS-app side)
• Tracking the user across the install gap (that's #75's job, and explicitly NOT this issue's)

References

• App Clip approach for first-install context: variablefate/roadflare-ios#75
• Custom URL scheme this banner uses: PR variablefate/roadflare-ios#66 (closes variablefate/roadflare-ios#64)
• Universal Links (long-term replacement for needing Smart App Banner at all once applinks is wired): variablefate/roadflare-ios#63
• Apple docs: Promoting Apps with Smart App Banners