Add duration-aware sharding to Vitest

Normalized profile

What this task asks for

Add duration-aware sharding strategies and duration history handling for Vitest. Add and validate the 12 duration-aware sequence fields and serialize them to worker configuration. Read, migrate, expire, smooth, and cap duration history observations using project-relative normalized paths. Implement time, round-robin, affinity, and fallback sharding with deterministic tie-breaking. Apply slow-file isolation, affinity load accounting, and rebalance warnings with fixed ratio formatting. Sort by recorded duration when requested and record rounded final durations while preserving unrelated history entries. Resolve `balanceShardsByTime` to the time strategy only when compatible and otherwise force it off.