Fix mypy: type checked_args_cache as list[Optional[CheckedArgs]]

The cache was typed as list[object], causing mypy attr-defined errors
when accessing .args/.kwargs on the cached value. Use proper CheckedArgs
type and extract to a local variable for mypy narrowing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bartv

src/inmanta/ast/statements/call.py

@@ -25,6 +25,7 @@
 import inmanta.ast.type as InmantaType
 import inmanta.execute.dataflow as dataflow
 from inmanta import plugins
+from inmanta.plugins import CheckedArgs
 from inmanta.ast import (
     ExplicitPluginException,
     ExternalException,
@@ -138,7 +139,7 @@ def execute_call(
         queue: QueueScheduler,
         result: ResultVariable,
         *,
-        checked_args_cache: Optional[list[object]] = None,
+        checked_args_cache: Optional[list[Optional[CheckedArgs]]] = None,
     ) -> None:
         """
         Evaluate this statement, using the output of execute_args
@@ -195,7 +196,7 @@ def call_in_context(
         queue: QueueScheduler,
         result: ResultVariable,
         *,
-        checked_args_cache: Optional[list[object]] = None,
+        checked_args_cache: Optional[list[Optional[CheckedArgs]]] = None,
     ) -> None:
         """
         Call this function in the supplied context and store the result in the supplied ResultVariable.
@@ -227,7 +228,7 @@ def call_in_context(
         queue: QueueScheduler,
         result: ResultVariable,
         *,
-        checked_args_cache: Optional[list[object]] = None,
+        checked_args_cache: Optional[list[Optional[CheckedArgs]]] = None,
     ) -> None:
         result.set_value(self.call_direct(args, kwargs), self.ast_node.location)
 
@@ -274,15 +275,16 @@ def call_in_context(
         queue: QueueScheduler,
         result: ResultVariable,
         *,
-        checked_args_cache: Optional[list[object]] = None,
+        checked_args_cache: Optional[list[Optional[CheckedArgs]]] = None,
     ) -> None:
 
-        if checked_args_cache is not None and checked_args_cache[0] is not None:
+        cached = checked_args_cache[0] if checked_args_cache is not None else None
+        if cached is not None:
             # Reuse validated args from a previous call (reschedule after UnsetException).
             # Type validation and domain conversion are deterministic for the same inputs,
             # and the DynamicProxy wrappers remain valid since they read from the same
             # underlying entity instances.
-            processed_args = checked_args_cache[0]
+            processed_args = cached
         else:
             processed_args = self.plugin.check_args(args, kwargs)
             no_unknows = not processed_args.unknowns
@@ -359,7 +361,7 @@ def __init__(
         # Cache for validated plugin arguments, reused across reschedules to avoid
         # redundant type validation when a plugin is retried after UnsetException.
         # Single-element list used as a mutable slot that can be written to by call_in_context.
-        self._checked_args_cache: list[object] = [None]
+        self._checked_args_cache: list[Optional[CheckedArgs]] = [None]
 
     def execute(self) -> None:
         # Execution in two stages to prevent re-execution of argument expressions