feat(headroom): add proxy lifecycle management + dashboard UI

Build on the optional Headroom Token Saver from Carmelo Campos
(PR: feat: add optional Headroom token saver). Add managed start/stop
of the local headroom proxy from the dashboard, install detection,
status probing, and a simplified Token Saver UI.

- detect headroom CLI + python>=3.10, probe proxy /health
- spawn/stop proxy as a detached, pid-tracked process
- /api/headroom/{status,start,stop} routes, gated local-only in dashboardGuard
- one-click Start/Stop Headroom modal, no manual config needed
- claude<->openai shape conversion for /v1/compress via 9router translators

Thanks to Carmelo Campos (@carmelogunsroses) for the original Headroom integration.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lib/headroom/detect.js

@@ -0,0 +1,63 @@
+import { execSync } from "child_process";
+
+const EXTENDED_PATH = `/usr/local/bin:/opt/homebrew/bin:/usr/bin:/bin:${process.env.PATH || ""}`;
+const PYTHON_CANDIDATES = ["python3.13", "python3.12", "python3.11", "python3.10", "python3"];
+const MIN_VERSION = [3, 10];
+const HEADROOM_HEALTH_TIMEOUT_MS = 1500;
+
+// Detect whether the headroom CLI is installed and where its binary lives.
+export function findHeadroomBinary() {
+  try {
+    const path = execSync("which headroom", {
+      stdio: ["ignore", "pipe", "ignore"],
+      windowsHide: true,
+      env: { ...process.env, PATH: EXTENDED_PATH },
+    }).toString().trim();
+    return path || null;
+  } catch {
+    return null;
+  }
+}
+
+// Find a Python interpreter >= 3.10 (headroom-ai requires it). Returns null if none.
+export function findPython310() {
+  for (const candidate of PYTHON_CANDIDATES) {
+    try {
+      const ver = execSync(`${candidate} --version`, {
+        stdio: ["ignore", "pipe", "ignore"],
+        windowsHide: true,
+        env: { ...process.env, PATH: EXTENDED_PATH },
+      }).toString().trim();
+      const match = ver.match(/(\d+)\.(\d+)/);
+      if (!match) continue;
+      const [major, minor] = [parseInt(match[1], 10), parseInt(match[2], 10)];
+      if (major > MIN_VERSION[0] || (major === MIN_VERSION[0] && minor >= MIN_VERSION[1])) {
+        return candidate;
+      }
+    } catch {
+      // candidate not present, try next
+    }
+  }
+  return null;
+}
+
+// Probe whether a Headroom proxy is reachable at the given URL by hitting /health.
+export async function probeProxyRunning(url) {
+  if (!url) return false;
+  const base = String(url).replace(/\/$/, "");
+  try {
+    const res = await fetch(`${base}/health`, { signal: AbortSignal.timeout(HEADROOM_HEALTH_TIMEOUT_MS) });
+    return res.ok;
+  } catch {
+    return false;
+  }
+}
+
+// Aggregate status for the dashboard: installed, running, python interpreter.
+export async function getHeadroomStatus(url) {
+  const path = findHeadroomBinary();
+  const python = findPython310();
+  const installed = Boolean(path);
+  const running = installed ? await probeProxyRunning(url) : false;
+  return { installed, path, running, python };
+}