feat(host-agent): default planner transport to cloud

openspec/changes/cloud-planner-proxy/tasks.md

@@ -46,7 +46,7 @@
 
 ## 3. Host Agent: cloud-proxy transport
 
-- [x] 3.1 Add `AI_PLANNER_TRANSPORT` (`direct` default | `cloud`) to
+- [x] 3.1 Add `AI_PLANNER_TRANSPORT` (`cloud` default | `direct`) to
       `apps/device-host-agent/host_agent/config.py`.
       Done: `HostAgentConfig.ai_planner_transport` +
       `_parse_ai_planner_transport`.
@@ -70,11 +70,10 @@
 
 - [x] 4.1 Update `apps/device-host-agent/host_agent/execution.py`'s
       `_host_agent_planner_config()`/`create_task_runner()` so that when
-      `AI_PLANNER_TRANSPORT=cloud`, the constructed `TaskRunner`'s
+      `AI_PLANNER_TRANSPORT` is unset or set to `cloud`, the constructed `TaskRunner`'s
       `AIPlanner` is built with a `CloudProxyToolCallingClient` instead of
-      the default local provider client, while leaving the existing
-      default-enabled/direct-transport behavior unchanged when
-      `AI_PLANNER_TRANSPORT` is unset or `direct`.
+      the local provider client, while `AI_PLANNER_TRANSPORT=direct` remains
+      an explicit direct-to-provider fallback.
       Done: new `_host_agent_planner()` helper + `host_agent_config` param
       threaded through `create_execution_factories()` from
       `app.py::create_application()`. Manually verified both transports
@@ -106,11 +105,10 @@
       (7 tests, using `httpx.MockTransport` -- success, screenshot
       base64-encoding, network error, structured 502 error, unstructured
       error response, and client-ownership on `close()`).
-- [x] 5.4 Unit tests for Host Agent wiring: `AI_PLANNER_TRANSPORT=cloud`
-      constructs an `AIPlanner` using `CloudProxyToolCallingClient`;
-      `AI_PLANNER_TRANSPORT` unset or `direct` preserves existing
-      direct-to-provider construction (no regression to the
-      already-implemented default-enabled behavior).
+- [x] 5.4 Unit tests for Host Agent wiring: `AI_PLANNER_TRANSPORT` unset or
+      set to `cloud` constructs an `AIPlanner` using
+      `CloudProxyToolCallingClient`; explicit `direct` preserves local
+      provider construction.
       Done: added to `apps/device-host-agent/tests/test_execution.py`
       (2 new tests, one parametrized over `None`/`"direct"`).
 - [x] 5.5 Full non-integration suite (`uv run --all-packages pytest -m
@@ -136,3 +134,9 @@
       full non-integration suite (492 passed); `python -m compileall` clean
       for `packages/cloud-platform/cloud`, `apps/cloud-api`,
       `apps/device-host-agent`.
+
+## 8. Default transport amendment
+
+- [x] 8.1 Make `cloud` the Host Agent default for
+      `AI_PLANNER_TRANSPORT`, retain `direct` as an explicit fallback, and
+      update the runtime contract, deployment guidance, and regression tests.