bench: spawn 30.5→13.8 ms after #084 + #079 + #082 + #097 merge

Round-2 integration: time-budget quantum (#084), k-table emit (#079),
scratch buf pool (#082), module-aware mangling (#097/#102) all on dev.
Lake spawn now baseline (1.00) vs go 14.27x, rust tokio 2.60x.
msg + sha256 unchanged (callers not migrated yet).

Author: morphqdd

benchmark/results/spawn.md

@@ -1,5 +1,5 @@
 | Command | Mean [ms] | Min [ms] | Max [ms] | Relative |
 |:---|---:|---:|---:|---:|
-| `lake (cooperative, ExecCtx alloc)` | 30.5 ± 1.0 | 29.4 | 36.6 | 1.00 |
-| `go (goroutines, GOMAXPROCS=1)` | 341.0 ± 14.9 | 316.6 | 368.0 | 11.17 ± 0.60 |
-| `rust (tokio current_thread)` | 79.4 ± 2.0 | 76.8 | 86.9 | 2.60 ± 0.10 |
+| `lake (cooperative, ExecCtx alloc)` | 13.8 ± 0.7 | 13.0 | 19.1 | 1.00 |
+| `go (goroutines, GOMAXPROCS=1)` | 197.0 ± 7.7 | 185.4 | 211.9 | 14.27 ± 0.90 |
+| `rust (tokio current_thread)` | 35.8 ± 0.6 | 34.8 | 38.4 | 2.60 ± 0.13 |