Phase 1 sub-commit 6: skeleton wiring — make dev runs end-to-end

Symfony app under framework/skeleton/symfony/: minimal bin/console,
public/index.php, MicroKernel-based src/Kernel.php, services.yaml,
framework/security/mercure config, and a demo App\Controller\PingController
that GETs /api/ping (returning JSON pong) and republishes the same
payload to the Mercure topic app://ping. composer.json uses a path
repository to symlink the bundle from ../../php so local edits are
picked up live.

QML app under framework/skeleton/qml/: top-level CMake that
add_subdirectory's framework/qml, a main.cpp that creates the Qt
process, runs SingleInstance.acquireOrForward before any QML loads,
exposes SingleInstance via context property, and loadFromModule's
Skeleton.Main. Main.qml uses BackendConnection / RestClient /
MercureClient from PhpQml.Bridge and renders status dots, a Ping
button, and an event log.

Caddyfile binds 127.0.0.1:8765, enables in-memory Mercure with a
256-bit dev JWT (matches symfony/.env, lcobucci/jwt requires this).
Makefile wraps build / dev / doctor / clean; scripts/dev.sh starts
FrankenPHP --watch and the Qt host together with explicit PID-based
teardown (process-group `kill 0` proved unreliable when frankenphp's
watch fork reparented).

Bug fixes uncovered in this sub-commit:
- SingleInstance.acquireOrForward: probe-first, then removeServer +
  retry-listen. The original loop-with-removeServer-after-failed-bind
  silently exited on stale sockets from prior runs.
- Main.qml: MercureClient does NOT inherit BackendConnection.token —
  Mercure subscribes anonymously in dev (Caddyfile), and forwarding
  the bridge bearer made it 401-loop.
- /api/ping was 500ing because the dev MERCURE_JWT_SECRET was 144 bits;
  bumped to 64-char (>=256 bit) to satisfy lcobucci/jwt.
- Linked the framework lib (php_qml_bridge) explicitly in addition to
  the QML plugin so SingleInstance.h resolves.
- Auto-generated config/reference.php gitignored.

Smoke verified offscreen: /healthz 200, /api/ping 200, 1 publish, 1
subscriber, zero 401s, clean shutdown with no zombies.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

framework/qml/src/SingleInstance.cpp

@@ -31,14 +31,10 @@ bool SingleInstance::acquireOrForward(const QStringList& launchArgs)
 {
     const QString name = endpointName();
 
-    for (int attempt = 0; attempt < kBindRetries; ++attempt) {
-        if (m_server.listen(name)) {
-            return true;  // we are the live instance
-        }
-
-        // Bind failed. Either a real instance is running (forward args), or
-        // a stale socket/pipe is left over from a crashed process (clean up
-        // and retry). Distinguish by trying to connect.
+    // Probe first: if a live instance answers, forward and exit.
+    // This avoids a race where eagerly calling removeServer() would break
+    // a running peer.
+    {
         QLocalSocket probe;
         probe.connectToServer(name);
         if (probe.waitForConnected(kForwardConnectTimeoutMs)) {
@@ -50,16 +46,24 @@ bool SingleInstance::acquireOrForward(const QStringList& launchArgs)
             probe.disconnectFromServer();
             return false;
         }
+    }
 
-        // No live peer responding — likely stale socket. Remove and retry
-        // with a brief backoff (PLAN.md §3 *Edge cases — Single-instance
-        // launch race*).
-        QLocalServer::removeServer(name);
+    // No live peer answered. The endpoint may not exist, or a stale
+    // file is left over from a crashed process — removeServer() handles
+    // both cases safely.
+    QLocalServer::removeServer(name);
+
+    for (int attempt = 0; attempt < kBindRetries; ++attempt) {
+        if (m_server.listen(name)) {
+            return true;
+        }
         QThread::msleep(kBindRetryDelayMs);
     }
 
-    // Exhausted retries without binding and without a live peer. Better to
-    // act as the live instance than to deadlock both processes into exiting.
+    // Exhausted retries — better to continue as a degraded "live" instance
+    // than to deadlock-exit (PLAN.md §3 *Edge cases — Single-instance
+    // launch race*). Subsequent invocations may not be forwarded, but
+    // this process will still run.
     return true;
 }