add FIREFOX_USE_CONTENT_SCRIPT_PROXY runtime flag

@@ -0,0 +1,47 @@1+/**2+ * passkey-flags.ts — single switch for the Firefox passkey content-script proxy.3+ *4+ * FIREFOX_USE_CONTENT_SCRIPT_PROXY5+ *6+ * true  — Use the content script monkey-patch (current workaround).7+ *         Required until Mozilla ships webAuthenticationProxy in stable Firefox.8+ *9+ * false — Use the native webAuthenticationProxy path (Chrome today; future10+ *         Firefox once the API ships).11+ *12+ * The value is computed at runtime from feature presence, not a hard-coded13+ * boolean. The day Firefox exposes `chrome.webAuthenticationProxy`, this flag14+ * flips to false on updated browsers without any code change. Cleanup at that15+ * point is purely subtractive — see the removal checklist below.16+ *17+ * TO REMOVE THE MONKEY-PATCH:18+ *   1. Confirm `webAuthenticationProxy` is in stable Firefox (not Nightly)19+ *      and the minimum supported Firefox version for Peach covers it.20+ *   2. Verify this flag evaluates to `false` automatically on the new build.21+ *   3. Delete src/content/passkeys-firefox.ts22+ *   4. Delete src/content/passkeys-firefox-relay.ts23+ *   5. Delete src/shared/passkey-flags.ts24+ *   6. Remove the PASSKEY_HAS_CREDENTIALS handler in src/background/messages.ts25+ *      and the Firefox branches in PASSKEY_CREATE / PASSKEY_GET handlers.26+ *   7. Remove the two Firefox content_scripts entries from manifest.firefox.json27+ *      and add `"webAuthenticationProxy"` to its permissions list.28+ *   8. The Chrome webAuthenticationProxy path already handles everything.29+ *30+ * Track removal readiness:31+ *   https://github.com/w3c/webextensions/issues/  (WECG passkey API issue)32+ */33+export const FIREFOX_USE_CONTENT_SCRIPT_PROXY: boolean = (() => {34+  // chrome.webAuthenticationProxy presence wins over everything — that path35+  // is preferred when available, regardless of how we got here.36+  const c = (typeof chrome !== "undefined" ? chrome : undefined) as37+    | { webAuthenticationProxy?: unknown; runtime?: { getURL?: (path: string) => string } }38+    | undefined;39+  if (c?.webAuthenticationProxy) return false;40+41+  try {42+    const url = c?.runtime?.getURL?.("") ?? "";43+    return url.startsWith("moz-extension://");44+  } catch {45+    return false;46+  }47+})();