feat: param_value context — enum/allowed completions for principalType, environmentType etc.

- Add _KNOWN_ENUMS dict (principalType, principalObjectType, environmentType fallbacks)
- Add param_value_completion_items() to BicepModuleCatalog
- Detect 'param_value' context in _detect_context() (cursor after 'param: ' inside params block)
- Wire param_value into _inject_completions()
- 9 new unit tests (context detection, catalog allowed, known enum fallback, injection)
- Fix modules.py edit regression (param_completion_items was orphaned)
- All 35 tests pass

tests/test_proxy.py

@@ -240,7 +240,7 @@ def test_detect_param_context():
         "module myMod 'br/modules:roleassignments:1.1.x' = {",
         "  name: 'test'",
         "  params: {",
-        "    ",  # ← cursor here
+        "    ",  # ← cursor here (blank line, no param name yet)
         "  }",
         "}",
     ]
@@ -251,6 +251,124 @@ def test_detect_param_context():
     assert ctx["version"] == "1.1.x"
 
 
+def test_detect_param_value_context_no_quote():
+    """Cursor after 'principalType: ' (no opening quote) → param_value context."""
+    lines = [
+        "module myMod 'br/modules:roleassignments:1.1.x' = {",
+        "  params: {",
+        "    principalType: ",  # ← cursor at end
+        "  }",
+        "}",
+    ]
+    session = _make_session_with_doc(URI, lines)
+    # character = len("    principalType: ") = 19
+    ctx = session._detect_context(URI, {"line": 2, "character": 19})
+    assert ctx["type"] == "param_value"
+    assert ctx["module"] == "roleassignments"
+    assert ctx["param"] == "principalType"
+    assert ctx["has_open_quote"] is False
+
+
+def test_detect_param_value_context_open_quote():
+    """Cursor after 'principalType: \\'' → param_value with has_open_quote=True."""
+    lines = [
+        "module myMod 'br/modules:roleassignments:1.1.x' = {",
+        "  params: {",
+        "    principalType: '",  # ← cursor after opening quote
+        "  }",
+        "}",
+    ]
+    session = _make_session_with_doc(URI, lines)
+    ctx = session._detect_context(URI, {"line": 2, "character": 20})
+    assert ctx["type"] == "param_value"
+    assert ctx["has_open_quote"] is True
+
+
+def test_param_value_items_from_catalog_allowed():
+    """environmentType completions come from catalog 'allowed' field."""
+    BicepModuleCatalog._modules = [_make_module(
+        "roleassignments",
+        versions=["1.1.x"],
+        schema={"1.1.x": {"parameters": {
+            "environmentType": {"type": "string", "allowed": ["DEV", "TEST", "PROD"]},
+        }}},
+    )]
+    items = BicepModuleCatalog.param_value_completion_items(
+        "roleassignments", "1.1.x", "environmentType"
+    )
+    labels = [i["label"] for i in items]
+    assert labels == ["DEV", "TEST", "PROD"]
+    # Without open quote, insertText should wrap in quotes
+    assert items[0]["insertText"] == "'DEV'"
+
+
+def test_param_value_items_open_quote():
+    """When has_open_quote=True, insertText closes the quote but doesn't open one."""
+    BicepModuleCatalog._modules = [_make_module(
+        "roleassignments",
+        versions=["1.1.x"],
+        schema={"1.1.x": {"parameters": {
+            "environmentType": {"type": "string", "allowed": ["DEV", "TEST", "PROD"]},
+        }}},
+    )]
+    items = BicepModuleCatalog.param_value_completion_items(
+        "roleassignments", "1.1.x", "environmentType", has_open_quote=True
+    )
+    assert items[0]["insertText"] == "DEV'"
+
+
+def test_param_value_items_known_enum_fallback():
+    """principalType uses _KNOWN_ENUMS fallback when not in catalog."""
+    BicepModuleCatalog._modules = [_make_module(
+        "roleassignments",
+        versions=["1.1.x"],
+        schema={"1.1.x": {"parameters": {
+            "principalType": {"type": "string"},  # no 'allowed' in catalog
+        }}},
+    )]
+    items = BicepModuleCatalog.param_value_completion_items(
+        "roleassignments", "1.1.x", "principalType"
+    )
+    labels = [i["label"] for i in items]
+    assert "Group" in labels
+    assert "ServicePrincipal" in labels
+    assert "User" in labels
+
+
+def test_param_value_items_empty_for_free_string():
+    """A plain string param with no allowed values returns no completions."""
+    BicepModuleCatalog._modules = [_make_module(
+        "roleassignments",
+        versions=["1.1.x"],
+        schema={"1.1.x": {"parameters": {
+            "principalId": {"type": "string"},
+        }}},
+    )]
+    items = BicepModuleCatalog.param_value_completion_items(
+        "roleassignments", "1.1.x", "principalId"
+    )
+    assert items == []
+
+
+def test_param_value_injected_in_completion_response():
+    """Full pipeline: param_value context injects enum completions at top."""
+    BicepModuleCatalog._modules = [_make_module(
+        "roleassignments",
+        versions=["1.1.x"],
+        schema={"1.1.x": {"parameters": {
+            "environmentType": {"type": "string", "allowed": ["DEV", "TEST", "PROD"]},
+        }}},
+    )]
+    msg = _completion_response([{"label": "existing", "sortText": "z"}])
+    ctx = {"type": "param_value", "module": "roleassignments", "version": "1.1.x",
+           "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
+
+
 def test_detect_unknown_context_outside_module():
     lines = ["var x = 'hello'"]
     session = _make_session_with_doc(URI, lines)