fix(dfir_lang): fix lattice_reduce dropping write_tick_end, use fully qualified RefCell::take

- Fix lattice_reduce to pass through write_tick_end from the delegated
  reduce operator (was silently dropped by `..` destructuring pattern).
- Use fully qualified `RefCell::take()` syntax in state_by tick reset
  for clarity.
- Remove `#[non_exhaustive]` from OperatorWriteOutput and add doc comment
  warning against using `..` in destructuring patterns for delegating
  operators.

Co-authored-by: Infinity 🤖 <infinity@hydro.run>

Author: MingweiSamuel

dfir_lang/src/graph/ops/mod.rs

@@ -111,8 +111,9 @@ impl Debug for OperatorConstraints {
 }
 
 /// The code generated and returned by a [`OperatorConstraints::write_fn`].
+/// **Important**: When destructuring this struct in delegating operators, list all fields
+/// explicitly rather than using `..` to ensure new fields are not silently dropped.
 #[derive(Default)]
-#[non_exhaustive]
 pub struct OperatorWriteOutput {
     /// Code which runs once outside any subgraphs, BEFORE subgraphs are initialized,
     /// to set up any external state (state API, chanels, network connections, etc.)