[trissim]

This PR moves field semantics out of Toad's Textual backend and into formbridge. A second backend (pyqt-reactive) can then read them without restating them. The Toad settings-menu PR (OpenHCSDev/toad, branch `work/toad-settings-menu`) depends on this one and imports `formbridge.forms.declared_fields`.

What moved (from toad/forms, deleted there)

`src/formbridge/forms/declared_fields.py`:

• `DeclaredField` and `OptionalMemberField`: label, help (cleandoc of the docstring), default, metadata lookup, validation before edit, edit through ObjectState. Formerly `toad/forms/declared_views.py:76-163`.
• `declarations(annotation)` and `DeclaredViews`. `DeclaredViews` is the registry a backend's widget family uses to choose a widget for each declared kind (`shows = (int,)`). Formerly `declared_views.py:26-74`.
• `FieldPath`, `declared_annotation`, `declared_type`. Formerly `toad/forms/field_path.py`.
• `Placeholder` and `Multiline` kinds. Formerly `toad/forms/kinds.py`.
• `DeclaredField.search_text`, the field's label plus the labels of the groups that contain it. Formerly computed in Toad's `ValueView.init`.

New facts read from the declaration

• Bounds: `DeclaredField.interval` merges every annotated_types `Ge/Gt/Le/Lt/Interval` into one `Interval`, reading each bound by its `Interval` field name, so no class list is kept. `bounds_text` renders it, e.g. `>= 1, <= 10`. Toad shows it under the help text. pyqt-reactive's `RangeConfigurable` can now be fed real bounds instead of its hard-coded ±999999 (`widget_strategies.py:473-477`).
• Pages: `FormPage` is `Annotated` metadata on a top-level group: `Annotated[UiSettings, INTERFACE]`. `form_pages(state, shown)` derives the tabs and their order from the fields that name them. A paged form that leaves a top-level field without a page raises `TypeError`.

Backend interface

A backend implements two `DeclaredViews` families:

• field views: one per formbridge `ParameterInfo` kind (value or nested group);
• value editors: one per declared kind (bool, int, float, str, `Multiline`, `AnnotationChoices`, `Enum`, `Optional`).

It also draws one tab per `FormPage`. The editors call `DeclaredField.edit`, and ObjectState owns values and dirty marks. Toad's Textual implementation lives in `toad/forms/{form_view,editors,presentation}.py`.

Checks

• New tests: `tests/test_declared_fields.py` covers bounds merging, search text, page order and refusal of an unpaged field. I executed the four functions directly in the agent-comms runtime interpreter (pytest is not installed there), and all four passed. `ruff check` passes on both new files.
• NRA (shared checkout, 97 detectors, `complete: true`, 0 omitted) on this branch: 0 findings name `declared_fields`.
• Not run: the full pytest suite (CI runs it).

Next, not in this PR

• pyqt-reactive is still on formbridge `>=0.1.3,<0.2` with `objectstate<4`. It cannot read these until it moves to 0.2/ObjectState 5.
• Both backends still hand-code dirty-mark glyphs and ancestor propagation, value-kind widget selection (pyqt's if-chain at `widget_strategies.py:842-906`), and the "Pipeline default:" placeholder text.
• `ui_hidden` is still a string-keyed metadata flag (`parameter_form_service.py:284`). It should become a declared kind.
• Not applied: the 4 formbridge codemods in claude-nra's ranked list (`1ea58902e5`, `51ad6c5e21`, `daa4e87a6d`, `fcae361a8e`). They concern bridge DTOs, not settings, and need NRA #124.

🤖 Generated with Claude Code

https://claude.ai/code/session_01RnH6dR85kyFKcc2tQAJLhK

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