fix(mumble): widen handshake readiness budget 60s->180s (load flake stabilization)

The TCP READY_PROBE proves 64738 is listening, but the murmur control channel needs more warmup to
complete a full TLS+ServerSync handshake; under concurrent sweep load that exceeded the 60s budget
(green in isolation, red under load). Longer budget absorbs the delay; assertions unchanged (a dead
server still fails after all retries).

tests/mumble/custom/test_protocol_handshake.py

@@ -19,7 +19,14 @@ import _mumble_proto  # noqa: E402
 
 
 def test_handshake_completes_with_channel_presence(live_app):
-    r = _mumble_proto.retry_handshake(attempts=12, interval=5.0)
+    # Readiness budget: 36×5s = 180s. The TCP READY_PROBE (recipe_meta) only proves port 64738 is
+    # LISTENING; the murmur control channel needs additional warmup before it completes a full
+    # TLS+Version+ServerSync handshake. Under concurrent node load (the canon sweep) that warmup
+    # exceeded the old 60s budget and flaked this test RED, while it is reliably GREEN in isolation
+    # (phase redfix M1: 3× isolation green, 0 isolation reds). The longer budget absorbs the
+    # load-induced readiness delay WITHOUT weakening the assertion — a genuinely non-responsive
+    # server still exhausts all retries and FAILs (the asserts below are unchanged).
+    r = _mumble_proto.retry_handshake(attempts=36, interval=5.0)
 
     assert r["tls_connect"], f"TLS connection to 127.0.0.1:64738 failed — {r.get('error')}"
     assert r["server_version"] is not None, "server did not send a Version message"