fix(traits): carry trait state and parameter callbacks through a save

[collindutter]

A parameter created at run time was saved as scalar fields only, so its traits and their
callbacks were dropped: a dynamically added dropdown reloaded as a bare field, a button reloaded
inert. Trait state on a declared parameter survived only because Parameter.ui_options was saved
merged, which is why Options and MultiOptions mirrored their choices into the parent's
ui_options.

Closes #5440.

A trait's fields are its saved contract

BaseNodeElement is an attrs class and its metaclass makes every element
one, so a trait declares fields and gets a constructor. Those fields are what a save writes.

class Threshold(Trait):
    level: int = attrs.field(default=5, alias="threshold")                    # state, saved as data
    on_cross: Callable | None = attrs.field(default=None, metadata=BEHAVIOR)  # saved by method name
    rendered: str = attrs.field(default="", init=False)                       # neither, not saved

The declaration is checked when the class is built, so a mistake costs a library its import
rather than an artist's saved work:

class Broken(Trait):
    root: Path | None = attrs.field(default=None)        # TypeError: no saved form
    on_ping: Callable | None = attrs.field(default=None)  # TypeError: declare metadata=BEHAVIOR
    level: int = 5                                        # TypeError: an annotation is not a field

Breaking for library authors: element fields are keyword-only, so Slider(0, 100) becomes
Slider(min_val=0, max_val=100), and elements compare by identity. MIGRATION.md covers both.

A trait owns the ui_options keys it renders

The ui_options getter overlays what traits render on top of stored options,
authored_ui_options() is the stored and saved view, and update_ui_options reads that rather
than the merged getter.

# before: parameter.hide = True also stored every trait's rendered options
ui_options = self.ui_options  # merged: trait options + stored options
ui_options[key] = value
self.ui_options = ui_options  # stored: now holds the trait's options too

Narrowing a Slider moved its validator but not the slider the artist sees, so the UI offered
values the engine rejected. Every hide, hide_label, display_name, markdown, collapsed,
and orientation write went through that path.

A write arriving from the editor or a saved file is routed to the trait that owns the key, since
neither writer knows which keys a trait owns:

parameter.update_ui_options({"slider": {"max_val": 8}})  # routed to the Slider
trait.max = 8  # same result, said directly

A trait declares what it accepts back with state_from_ui_options, the inverse of
ui_options_for_trait; Options, MultiOptions, and Slider are the three of thirteen that
need it. A write to a rendered key no trait accepts is logged, since it is neither applied nor
saved.

Serialize trait identity and state

to_state/from_state/apply_state, carried on AddParameterToNodeRequest.traits and on the
traits field AlterParameterDetailsRequest has always declared but never applied.

Slider(min_val=0, max_val=8).to_state()  # {"min_val": 0, "max_val": 8}

Restoring goes through the real constructor, so whatever invariants it enforces still hold, and it
updates the trait the node's __init__ already built instead of replacing it, so a button's
on_click survives and a field absent from an older file keeps its default. A saved trait is
paired with its class by module and name, so two libraries can ship a trait of the same name; a
library's process-local module name is saved as its stable namespace. migrate_state runs once per
load, so an override may rename or convert unconditionally.

Saving writes only the options authored on the parameter, which lets both choices workarounds and
their CRITICAL: comment blocks go.

Carry callbacks by method name

A callback is recorded as the name of a method on the owning node and resolved with a getattr on
that node at load, so the restored callback binds to the node doing the loading rather than the one
that was saved.

Button(label="Run", on_click=self.run)
# saved as: trait_callbacks={"on_click": "run"}

Parameter(name="tag", tooltip="t", converters=[self.strip_padding])
# saved as: value_callbacks={"converters": ["strip_padding"]}

A lambda has no name to resolve, so it is refused rather than guessed at, and reported at save
time. Each list is all-or-nothing: restoring a subset of a converter chain would run a different
pipeline than the one that was saved while appearing to work.

Degrade instead of failing

An unresolvable trait name, saved state missing a required constructor argument, and a trait that
cannot account for one of its own arguments are each logged and skipped. All three are
library-authoring mistakes an artist cannot fix, so losing one control beats failing the whole
load, or the whole save.

Workflows already on disk

A file that predates trait state carries a dropdown's choices in ui_options, since that was the
only field a save wrote, and they are adopted onto the trait the node built. A parameter the node
created at run time has no trait to adopt them onto, so it is rebuilt from them:

{"simple_dropdown": [...]}  # or enum_choices, its older spelling -> Options
{"multi_options": {...}}    # -> MultiOptions
{"slider": {...}}           # -> Slider

Those are the only keys a save could round-trip. A missing traits field marks a file as predating
trait state; an empty one is a current save saying the parameter has no traits.

---

📚 Documentation preview 📚: https://griptape-nodes--5523.org.readthedocs.build/en/5523/

[codecov]

Codecov Report

❌ Patch coverage is 90.47619% with 76 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ptape_nodes/retained_mode/managers/node_manager.py	91.53%	11 Missing ⚠️
...pe_nodes/exe_types/param_types/parameter_button.py	43.75%	9 Missing ⚠️
src/griptape_nodes/exe_types/callback_binding.py	78.57%	6 Missing ⚠️
src/griptape_nodes/exe_types/trait_state.py	95.14%	5 Missing ⚠️
...ape_nodes/exe_types/param_types/parameter_audio.py	0.00%	4 Missing ⚠️
...ape_nodes/exe_types/param_types/parameter_image.py	0.00%	4 Missing ⚠️
...tape_nodes/exe_types/param_types/parameter_json.py	0.00%	4 Missing ⚠️
...pe_nodes/exe_types/param_types/parameter_string.py	0.00%	4 Missing ⚠️
...ape_nodes/exe_types/param_types/parameter_video.py	0.00%	4 Missing ⚠️
...ptape_nodes/exe_types/param_types/parameter_xml.py	0.00%	4 Missing ⚠️
... and 13 more

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