Compatibility with pyiron_workflow==0.19.2

[Copilot]

pyiron_workflow 0.19.x is a ground-up redesign: nodes are now immutable recipe-based objects backed by flowrep, ports have no mutable .value, wf.children is gone, NOT_DATA moved to flowrep, and the old Function/Macro/DataclassNode class hierarchy no longer exists. This PR updates pyironFlow to work with the new API.

Core architectural changes

• Port values — ports are now frozen dataclasses with no .value. Input values are stored as hidden Constant nodes (prefixed _const_) connected via edges. A new apply_node_values() helper creates/wires these after a node is added to the workflow. Values are read back by inspecting connected constant nodes or recipe defaults.
• Node construction — replaced NodeClass(label=...) with atomictype2node(func, label). Import paths now come from node.recipe.fully_qualified_name.
• Edges — replaced wf.graph_as_dict["edges"]["data"] with wf.edges (list of EdgeTuple(source, target) with .node/.port fields). Node connections use wf.connect(out_port, in_port) instead of inp.connect(out).
• Workflow mutation — wf.children → wf.nodes, add_child/remove_child → add_node/remove_node, wf.disconnect(node) replaces per-port disconnect.
• Run status — node.failed/node.running replaced by inspecting wf.last_run.steps per node label. Output values read from wf.last_run.result.nodes[label].output_ports.

File-by-file

• themes.py — imports and isinstance checks updated to Atomic, Macro, Workflow, Constant; removed node.color fallback.
• wf_extensions.py — rewrote get_nodes, get_edges, get_node_dict, dict_to_node, dict_to_edge, get_import_path; added apply_node_values; all channel_dict references replaced with direct dict iteration.
• reactflow.py — updated imports, add_node, get_workflow, get_selected_workflow; SAVE/LOAD/DELETE stubs with informative messages (API removed upstream); removed ReadinessError/ChannelConnectionError handlers; default wf parameter moved out of signature (new API rejects keyword label=).
• pyproject.toml — pyiron_workflow pinned to 0.19.2.

Example: creating and running a workflow

import flowrep as fr
from pyiron_workflow import Workflow
from pyiron_workflow.constructors import atomictype2node

@fr.atomic
def add(x: float, y: float) -> float:
    return x + y

wf = Workflow("demo")
n = atomictype2node(add, "n1")
wf.add_node(n)
# Values supplied via hidden constant nodes automatically managed by pyironFlow