refactor(layout): move change detection into resolved layout stage

[tupizz]

Summary

• Add version field to all resolved item types
• Create versionSignature.ts and hashUtils.ts in layout-resolved (moved from painter)
• deriveBlockVersion() and fragmentSignature() now compute during resolution
• Painter uses resolved version for change detection with legacy fallback

PR Stack (SD-2563: Dumb Painter Refactor)

#	PR	Title	Status
1	#2810	Lift page metadata into ResolvedPage
2	#2811	Lift fragment metadata into resolved paint items
3	#2812	Pre-compute SDT container keys in resolved layout
4	#2813	Pre-compute paragraph border data in resolved layout
5	#2814	Move change detection into resolved layout stage	👈 this PR
6	#2818	Lift paragraph/list block and measure into resolved items
7	#2819	Extract block/measure resolution helper
8	#2820	Remove body blocks/measures from DomPainterInput

Test plan

• 94/94 layout-resolved tests pass (10 new)
• painter-dom types compile cleanly
• No rendering behavior changes

[linear]

SD-2563 Painter refactor: clear inputs/outputs - "dumb" painter