fix(2): Q4.2 mumble — provide host-ports overlay for every version via install_steps

The upstream compose.host-ports.yml exists only from v1.0.0+, but the upgrade-tier base deploy is
the previous published version (0.2.0+), which predates it — so EXTRA_ENV's COMPOSE_FILE failed to
resolve on the base deploy (config --images rc=14, deploy FATA). install_steps.sh now copies a
cc-ci-owned identical overlay into the recipe checkout when absent, so 64738 is host-published for
every version (base + upgrade) and on-host protocol tests reach 127.0.0.1:64738.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/mumble/compose.host-ports.yml

@@ -0,0 +1,19 @@
+---
+# cc-ci-owned copy of the upstream mumble `compose.host-ports.yml` overlay (identical content).
+# Provided to the recipe checkout by tests/mumble/install_steps.sh so that 64738 is published on the
+# cc-ci host for EVERY version under test — the upstream overlay only exists from recipe version
+# 1.0.0+, but the upgrade tier's base deploy is the previous published version (0.2.0+), which
+# predates it. On-host tests (cc-ci-run) reach the voice server at 127.0.0.1:64738 via this publish.
+version: "3.8"
+
+services:
+  app:
+    ports:
+      - target: 64738
+        published: 64738
+        protocol: tcp
+        mode: host
+      - target: 64738
+        published: 64738
+        protocol: udp
+        mode: host