Protocol: Add DetailView display hints — hideEmpty, primaryField, summaryFields, collapseWhenEmpty

[hotlong]

Background

Based on a platform-wide DetailView UX audit (see cross-repo issue in objectstack-ai/objectui), the current spec schemas lack several display-hint properties that renderers need to deliver intelligent default behavior. The protocol already has rich layout primitives (FormSectionSchema, RecordDetailsProps, RecordActivityProps, ResponsiveConfigSchema), but is missing a few critical fields that prevent renderers from optimizing empty-state, header, and activity panel behavior without hardcoding.

This issue covers protocol-only changes. The corresponding renderer consumption work is tracked in objectstack-ai/objectui.

Changes Required

1. FormSectionSchema — add hideEmpty + emptyPlaceholder

File: packages/spec/src/ui/view.zod.ts

Current:

export const FormSectionSchema = z.object({
 label: I18nLabelSchema.optional(),
 collapsible: z.boolean().default(false),
 collapsed: z.boolean().default(false),
 columns: z.enum(['1', '2', '3', '4']).default('2'),
 fields: z.array(z.union([z.string(), FormFieldSchema])),
});

Add:

 hideEmpty: z.boolean().optional()
 .describe('Hide fields with null/undefined/empty string values'),
 emptyPlaceholder: I18nLabelSchema.optional()
 .describe('Placeholder text for empty values when hideEmpty is false (default: "—")'),

Also consider adding 'auto' to the columns enum so renderers can infer optimal column count:

 columns: z.enum(['auto', '1', '2', '3', '4']).default('2'),

2. RecordDetailsProps — add hideEmpty, primaryField, summaryFields

File: packages/spec/src/ui/component.zod.ts

Add to existing RecordDetailsProps:

 hideEmpty: z.boolean().default(false)
 .describe('Hide fields with empty values in detail display'),
 primaryField: z.string().optional()
 .describe('Field name to use as record title in header (e.g. "name"). Renderer falls back to first text field or objectName.'),
 summaryFields: z.array(z.string()).max(5).optional()
 .describe('Key fields to render as badges/chips in the header area (e.g. ["status", "priority"])'),

3. RecordActivityProps — add collapseWhenEmpty, emptyActions

File: packages/spec/src/ui/component.zod.ts

Add to existing RecordActivityProps:

 collapseWhenEmpty: z.boolean().default(false)
 .describe('Auto-collapse activity panel when no feed items exist'),
 emptyActions: z.array(z.string()).optional()
 .describe('Quick-action IDs to surface when timeline is empty (e.g. ["log_call", "send_email"])'),

Tests to Add

File: packages/spec/src/ui/view.test.ts

• FormSectionSchema accepts hideEmpty: true
• FormSectionSchema accepts emptyPlaceholder string
• FormSectionSchema accepts columns: 'auto'
• Backward compat: existing schemas without new fields still parse

File: packages/spec/src/ui/component.test.ts

• RecordDetailsProps accepts primaryField, summaryFields, hideEmpty
• RecordActivityProps accepts collapseWhenEmpty, emptyActions
• Backward compat: RecordDetailsProps.parse({}) still works with defaults

Documentation Updates

• content/docs/references/ui/component.mdx — add new properties to RecordDetailsProps and RecordActivityProps tables
• content/docs/protocol/objectui/layout-dsl.mdx — add hideEmpty example in Section Definition
• content/docs/guides/metadata/view.mdx — add best-practice example showing hideEmpty + columns: 'auto'

Non-Breaking

All additions are optional fields with defaults — zero impact on existing schema consumers.

Cross-Repo

• objectstack-ai/objectui will track the renderer consumption of these new properties (cross-repo issue)