ocs_doc_api: Phase 5-ii — typed Table create

- CreateTable(TableSpec{insertion_point, data[row][col]}) op (append-only).
- backend add_table via Table::new(insertion_point, rows, cols) + set_cell_text
  (Table::default() pre-creates 3x3, so use Table::new for exact dims).
- executor validates non-empty rectangular grid; facade create_table.
- spec Table constructor; api_reference + binding_schema regenerated; mocks + baseline.
- Test phase5ii_create_table_from_grid (3x2 grid, non-rectangular rejected)
  -> 615 host lib + 3 consistency green. Phase 5 complete.

crates/ocs_doc_api/src/executor.rs

@@ -293,6 +293,17 @@ pub fn apply_op<B: DocApiBackend>(b: &mut B, op: Operation) -> ApiResult<Receipt
             b.finalize_op();
             OpOutcome::NewId(id)
         }
+        Operation::CreateTable(spec) => {
+            // Validate a non-empty, rectangular grid before committing.
+            let cols = spec.data.first().map(|r| r.len()).unwrap_or(0);
+            if spec.data.is_empty() || cols == 0 || spec.data.iter().any(|r| r.len() != cols) {
+                return Err(ApiError::validation(name, "table needs a non-empty rectangular grid"));
+            }
+            b.push_undo(name);
+            let id = b.add_table(spec)?;
+            b.finalize_op();
+            OpOutcome::NewId(id)
+        }
     };
     Ok(Receipt {
         outcome: Some(outcome),