[SDUI][P1] Unify list/grid views under PageSchema + viewType synthesis

[xuyushun441-sys]

Context

List/grid and the kanban/calendar/gantt/map view variants still use the legacy NamedListView model (ObjectView in app-shell wraps plugin-view/plugin-list). They are not unified under PageSchema + viewType synthesis the way record detail pages are. ViewConfigPanel only edits columns/filters/sort.

Goal

Bring list views into the same SDUI pipeline: a synthesized list PageSchema (by viewType) that can be assigned/overridden and rendered via SchemaRenderer.

Scope

• A buildDefaultListPageSchema(objectDef, viewType) synthesizer mirroring buildDefaultPageSchema.
• Route ObjectView through SchemaRenderer with a legacy fallback kill-switch.
• Preserve existing runtime column/filter/sort edits via the draft/publish seam.

Acceptance

• Grid + at least one alt viewtype (kanban) render via the schema path
• Author-assigned list page overrides the synthesized default
• Existing list-view runtime edits still persist
• Legacy NamedListView path retained behind a flag during migration