agent window: plain message when the endpoint wants a key

A 401/403 with an HTML error page (nginx) showed as "HTTP 401: 401
Authorization Required 401 Authorization Required nginx". Now: "The endpoint
wants an API key: enter it in ⚙" before one is set, "The endpoint refused
the API key (...)" after.

tools/agent_checks.py

@@ -121,7 +121,8 @@ def run(pg, objects, shot, check, can_set_key):
         settings()
         pg.locator("#agkey").fill("wrong-key")
         save()
-        check("401" in pg.locator("#agsetmsg").inner_text(), "a wrong key shows the endpoint's refusal: " + pg.locator("#agsetmsg").inner_text())
+        check("refused the API key" in pg.locator("#agsetmsg").inner_text() and "invalid api key" in pg.locator("#agsetmsg").inner_text(),
+              "a wrong key shows the endpoint's refusal: " + pg.locator("#agsetmsg").inner_text())
         check(pg.locator("#agwho .ag-off").count() == 1, "the status dot turns red")
         shot("agent-badkey.jpg")
         pg.locator("#agkey").fill("test-key")