fix(core): type slot render payloads

Tighten typed Slot::render and KeyedSlot append/prepend/replace helpers so callers pass the generated slot payload type, keeping explicit html/text escape hatches for deliberate conversions.

req: codegen/002

req: typed_id/001

slhx-test/tests/inspector.rs

@@ -21,7 +21,7 @@ fn inspects_tuple_effects() {
 #[test]
 fn finds_keyed_slot_targets() {
     let rows = KeyedSlot::<u32, String>::new(9);
-    let inspected = slhx_test::inspect(rows.append(7, "row"));
+    let inspected = slhx_test::inspect(rows.append(7, String::from("row")));
 
     assert!(inspected.has_keyed_slot(rows));
     assert_eq!(inspected.ops().len(), 1);