build: fail the release when smoke tests fail, and fix the SSE test that hung

release.sh printed `WARNING: Smoke tests failed!` and exited 0. That is how four
broken readiness probes shipped unnoticed on 2026-08-10 — the warning scrolled
past in the build log and the release reported success.

It now exits 1, with `MCPCTL_ALLOW_SMOKE_FAILURE=1` as the escape hatch. The
message is explicit that smoke runs LAST, against the installed binary: the
package is already published and installed, so the failure reports fleet
breakage rather than preventing a bad artifact.

Turning the gate on required fixing a latent hang first, or every release would
have blocked on it. `security.test.ts > /inspect SSE endpoint …` waited for a
response body that by design never ends, so it could only settle via the
socket's *inactivity* timeout — and /inspect relays every project's MCP traffic,
so during a full smoke run it is never idle. Run alone it passed and looked
flaky; run with the suite it failed every time.

httpRequest gains `headersOnly`, which resolves on the response headers and
hangs up. The assertion only ever needed the status line.

Verified: full smoke suite 158/158 (was 157/158 with this test timing out); the
gate block lifted verbatim from release.sh exits 1 with a stubbed failing smoke
run, and exits 0 reaching subsequent code under MCPCTL_ALLOW_SMOKE_FAILURE=1.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019wUmrfkVQR6CKcYKxENq7k

src/mcplocal/tests/smoke/security.test.ts

@@ -32,6 +32,18 @@ function httpRequest(opts: {
   headers?: Record<string, string>;
   body?: string;
   timeout?: number;
+  /**
+   * Resolve as soon as the response headers arrive, then hang up, instead of
+   * waiting for the body to end.
+   *
+   * Required for a streaming endpoint: SSE responses never end, so the normal
+   * path can only settle via the socket's *inactivity* timeout — which never
+   * fires while the stream is busy. `/inspect` relays every project's MCP
+   * traffic, so during a full smoke run it is never idle, and the request hung
+   * until vitest killed the test. Alone it looked flaky; under load it failed
+   * every time. Reading the status does not need the body anyway.
+   */
+  headersOnly?: boolean;
 }): Promise<{ status: number; headers: http.IncomingHttpHeaders; body: string }> {
   return new Promise((resolve, reject) => {
     const parsed = new URL(opts.url);
@@ -46,6 +58,12 @@ function httpRequest(opts: {
         timeout: opts.timeout ?? 10_000,
       },
       (res) => {
+        if (opts.headersOnly === true) {
+          resolve({ status: res.statusCode ?? 0, headers: res.headers, body: '' });
+          res.destroy();
+          req.destroy();
+          return;
+        }
         const chunks: Buffer[] = [];
         res.on('data', (chunk: Buffer) => chunks.push(chunk));
         res.on('end', () => {
@@ -93,17 +111,15 @@ describe('Smoke: Security — mcplocal unauthenticated endpoints', () => {
 
     // /inspect streams ALL MCP traffic (tool calls, arguments, responses)
     // for ALL projects to any unauthenticated local client
+    // headersOnly: the stream never ends, and waiting for it to go idle is what
+    // made this hang whenever other suites were generating traffic. The status
+    // line is all this assertion needs.
     const res = await httpRequest({
       url: `${MCPLOCAL_URL}/inspect`,
       method: 'GET',
       headers: { 'Accept': 'text/event-stream' },
       timeout: 3_000,
-    }).catch((err) => {
-      // Timeout is expected (SSE keeps connection open) — still means endpoint is accessible
-      if ((err as Error).message.includes('timed out')) {
-        return { status: 200, headers: {} as http.IncomingHttpHeaders, body: '' };
-      }
-      throw err;
+      headersOnly: true,
     });
 
     // Should be accessible without auth (documenting the vulnerability)