Fix sitemap scroll hitching under frequent long-poll updates

[timbms]

Summary

Fixes scroll hitching reported in #1136, introduced by the SwiftUI sitemap migration in 3.2.x.

Root cause: Every long-poll result unconditionally ran reconcileWidgets + copyWidgetProperties and always reassigned @Published rowInputs, broadcasting objectWillChange on every cycle even when nothing the list renders changed. Under frequently updating items this produced continuous main-thread churn during inertial scrolling.

Changes:

• Snapshot before mutate — updateUI now maps incoming page data to SitemapRowInput values before any widget object mutation. If the preview inputs equal the current rowInputs and the title is unchanged, the method returns immediately — skipping all reconciliation and every @Published write. When searchText is active, reconciliation still runs so currentPage stays fresh and clearing the filter doesn't reveal stale hidden rows.

• RowID-keyed widget versioning — widgetUpdateVersions is now keyed by RowID.rawValue (pageKey + widgetId + occurrence) instead of bare widgetId. This prevents repeated widget IDs on one page from suppressing each other's version advances. bumpWidgetVersions increments by full row-identity pairs. SliderRowView, SegmentedRowView, SelectionRowView, and ImageRowView pass input.rowID to the version lookup; the four affected row-input types (SliderRowInput, SegmentedRowInput, SelectionRowInput, MediaRowInput) carry their rowID.

• rowInputs equality guard — rebuildRowInputs (called on search-text changes and static init) skips the @Published assignment when the computed array equals the current one.

• Tests — SitemapPageViewModelDiffingTests covers: stable rebuild equality, objectWillChange suppression on unchanged data, structure-change rebuild, bumpWidgetVersions no-op on identical inputs, per-row version isolation, structure-change full bump, and repeated-widgetId independence (8 cases).

Test plan

• Build and run openHABTestsSwift/SitemapPageViewModelDiffingTests — all 8 cases pass
• Manual: open a sitemap with frequently updating items (temperature sensors, power meters), scroll quickly — verify no stutter
• Manual: use search field, scroll, clear search — verify rows reappear correctly with current state
• Manual: sliders, segmented controls, selection rows — verify interactive controls still sync with server state
• Manual: image/chart rows with refresh intervals — verify periodic reload still works