Tier 2 (#2901): spec values that validate and then render nothing

[os-zhuang]

From the #2901 audit (doc). This is the #2897 shape — validates at authoring time, renders nothing, no test fails and no warning fires.

Finding	Location	What happens
element: 'toggle' removes the entire filter bar	plugin-list/src/UserFilters.tsx:162	default: return null. See below — this one is worse than a gap.
7 chart types draw an empty plot	plugin-charts/src/AdvancedChartImpl.tsx:343	Grid, axes, tooltip and legend all render; every series mark hits return null. Indistinguishable from an empty dataset. Reachable because ChartRenderer.tsx:135 reads schema.chartType ?? spec.chartType, bypassing normalizeChartSchema's RENDERABLE gate.
6 of 9 animation presets do nothing	react/src/hooks/useAnimation.ts:64	PRESET_CLASSES is keyed in hyphens ('slide-up'), the spec enum in underscores (slide_up); rotate/flip absent entirely. Lookup misses → '' → no animation.
3 of 6 easings emit invalid CSS	react/src/hooks/useAnimation.ts:112	Same split, but EASING_MAP[easing] || easing falls through to the raw string: animationTimingFunction: 'ease_in_out'. Browser drops it; devtools shows the attribute populated.
mode: 'auto' breaks theming	app-shell/src/chrome/ThemeProvider.tsx:38, providers/src/ThemeProvider.tsx:33	Both branch on "system"; the spec says auto. root.classList.add('auto') matches no Tailwind variant → light theme, OS preference no longer followed, no error.
Export PDF downloads nothing	plugin-grid/src/ObjectGrid.tsx:1258, plugin-list/src/ListView.tsx:1611	Excluded from serverEligible, absent from the client fallback. Popover closes, no file. xlsx behaves the same whenever the server path is unavailable.
Timeline scale blanks the axis	plugin-timeline/src/renderer.tsx:270	hour/quarter/year produce zero header columns. All six are ignored entirely on the default vertical variant.
All 6 toast positions discarded	components/src/renderers/feedback/toaster.tsx:15	<SonnerToaster /> with no props, inputs: [].
All 5 notification types collapse to toast	react/src/context/NotificationContext.tsx:155	displayType is stored on the item and never read.
navigation.size ignored off app-shell	react/src/hooks/useNavigationOverlay.ts:27	Hook declares width, no size. Every non-app-shell host silently uses the default width.
date-range / text filters are dead controls	plugin-list/src/UserFilters.tsx:456	Chip renders; popover shows the literal "No options".
4 gesture types become tap	mobile/src/useSpecGesture.ts:49	Hook never reads config.type; branches on sub-object presence. pan/drag/rotate/double_tap match nothing and keep the 'tap' initializer.
Report aggregate: 'unique' → blank cell	plugin-report/src/ReportViewer.tsx:102	default: return ''. Textbook #2897.
9 field types get a plain text input inline	fields/src/FieldEditWidget.tsx:54	json, composite, record, repeater, tree, video, audio, autonumber — in neither EDIT_WIDGETS nor INLINE_EXCLUDED_FIELD_TYPES. (secret fixed in #2940.) Editing a structured value through a text box is a corruption path.
5 accepted filter operators never offered	components/src/custom/filter-builder.tsx:58	$startsWith, $endsWith, $notContains, $null, $exists are unreachable from the UI.

The one that is worse than a gap

ui/view.zod.ts:315 says of toggle: "Kept in the enum so existing configs keep rendering; do not author new toggle filters." The renderer returns null — the whole filter bar vanishes. The component's own docstring at UserFilters.tsx:122 advertises "toggle: on/off toggle buttons per field".

Three artifacts describe one value; the only one that executes is the one that says nothing. Either the spec's compatibility promise is false and should be withdrawn, or toggle needs a branch. This is a decision, not a patch.

Cheap wins

useAnimation.ts is a pure key-spelling fix — usePageTransition.ts in the same directory already uses the correct underscore vocabulary with all nine presets. Copy it.

Refs #2901