Value.Diff produces property-level diff payloads instead of relying
solely on prepareUpdate. Function-valued props are stripped before
diffing; ValueDiffError is caught and falls back to prepareUpdate.
Value.Equal and Value.Clone now safely handle function-valued props
with try-catch fallbacks.
Adds hash field to Fiber<I> for caching FNV-1a hash after each commit.
Hash comparison runs before Value.Equal in reconcileProps for fast bail-out
on unchanged subtrees. Hashes computed during commit phase only (outside
reactive computations) via commitHashes after commitEffects.
