fix: honest costs in streams, oracle-sized timeouts, history & log cleanup

Cost showed $0 for every streamed request: the X-Cortiq-Cost-USD header is
written before generation, when the cost cannot be known. The gateway now
ships the final number in a closing SSE event (`cortiq_cost_usd`, alongside
the token estimate when the provider sent no usage), and the console prefers
it over the header. Money renders with 4 decimals, the last two in a smaller
font — $0.0006 stays readable instead of collapsing to $0.

Timeouts, both ends: the router default was 800 ms, silently degrading every
prompt the hosted router escalates to its oracle (~10 s) — now 15 s. Provider
clients had NO timeout at all (a dead OpenRouter host hung requests forever) —
now a 10 s connect timeout, with no overall cap so long generations and
streams are never cut.

Benchmark history: per-run × and a Clear-all button. Logs view: a clear
button backed by DELETE /admin/api/logs.

web/js/ui.js

@@ -95,11 +95,22 @@ export function confirmDialog(message) {
 }
 
 // number formatting
+// Money as a DOM node: 4 decimals, the last two rendered smaller — tiny
+// per-request prices stay readable without shouting six zeros.
+export function moneyEl(n) {
+  if (n == null) return document.createTextNode("—");
+  if (n === 0) return document.createTextNode("$0");
+  const s = n.toFixed(4);
+  return h("span", { class: "money" }, "$" + s.slice(0, -2), h("small", { class: "money-tail" }, s.slice(-2)));
+}
+
 export function money(n) {
   if (n == null) return "—";
   if (n === 0) return "$0";
-  if (Math.abs(n) < 0.01) return "$" + n.toFixed(6);
-  return "$" + n.toFixed(4);
+  // up to 4 decimals, trailing zeros trimmed (but keep money-like 2 minimum)
+  let s = n.toFixed(4).replace(/0+$/, "").replace(/\.$/, "");
+  if (/\.\d$/.test(s)) s += "0";
+  return "$" + s;
 }
 export function ms(n) {
   return n == null ? "—" : `${Math.round(Number(n))} ms`;