fix(bicep): replace LS completions entirely for version/param/param_value contexts

For specific LRU contexts (version, param, param_value), the Bicep LS was
appending its own random/irrelevant completions alongside the LRU catalog
items. The LS has no knowledge of the private ACR registry, so its suggestions
in these positions are noise.

Now the LS items are discarded entirely for these three contexts. LS items
are still kept (below LRU items) for module_path and unknown contexts.

tests/test_proxy.py

@@ -102,9 +102,9 @@ def test_version_completions_injected_on_version_context():
     assert "1.1.x" in labels
     assert "2.0.x" in labels
     assert "latest" in labels
-    # LRU versions come first
-    assert items[0]["sortText"].startswith("0_lru_ver_")
-    assert items[-1]["sortText"].startswith("1_az_")
+    # LS items are replaced entirely — private registry versions only
+    assert all(i["sortText"].startswith("0_lru_ver_") for i in items)
+    assert not any(i["label"] == "az-builtin" for i in items)
 
 
 def test_version_items_include_param_detail():
@@ -366,9 +366,8 @@ def test_param_value_injected_in_completion_response():
            "param": "environmentType", "has_open_quote": False}
     out = json.loads(_inject_completions(msg, ctx))
     labels = [i["label"] for i in out["result"]["items"]]
-    # LRU enum values should be first
-    assert labels[:3] == ["DEV", "TEST", "PROD"]
-    assert "existing" in labels
+    # LRU enum values only — LS completions are replaced entirely
+    assert labels == ["DEV", "TEST", "PROD"]
 
 
 def test_detect_unknown_context_outside_module():