add resilient multi-engine browser discovery

README.md

@@ -1,8 +1,10 @@
 # Browser-only ProspectOS
 
 This is the stripped-down replacement for the larger ProspectOS application.
-It searches public engines (Google first, then Bing and DuckDuckGo if Google
-challenges the server) through a headless Playwright Chromium browser. Each
+It searches public engines (Google, Bing, DuckDuckGo, Brave Search, and
+Startpage) through a headless Playwright Chromium browser, moving to the next
+engine when a server-side challenge, timeout, or empty/changed result page is
+encountered. Each
 discovery run builds a query from category, keywords, and location, filters
 results already present in the local catalogue by root domain, and stores only
 new prospects. The explorer supports search and human review states
@@ -19,9 +21,19 @@ docker compose up -d --build
 
 Open `http://SERVER:8000`.
 
-If Google presents a CAPTCHA or bot challenge, the run fails safely. The app
-does not bypass challenges or rotate identities. Keep runs small and spaced
-out. The implementation uses a fresh headless browser context for each run.
+If another service already owns port 8000, choose the host port without
+changing the container:
+
+```bash
+HOST_PORT=8080 docker compose up -d --build
+```
+
+If an engine presents a CAPTCHA or bot challenge, the run moves on to the next
+engine. The app does not bypass challenges or rotate identities. Keep runs
+small and spaced out. The implementation uses a fresh headless browser
+context for each engine and unwraps normal search redirect links before
+deduplication. If every public engine blocks the server IP, the run reports a
+clear `search_engines_unavailable` error instead of inventing prospects.
 
 ## Run locally