perf(executors): prewarm pooled shells (#13)

Author: aallam

.changeset/true-prewarm-and-worker-pool-default.md

@@ -0,0 +1,8 @@
+---
+"@execbox/process": patch
+"@execbox/worker": patch
+---
+
+Improve pooled executor warmup so `prewarm()` runs a real no-op QuickJS session inside each warmed shell before it is returned to the pool. This reduces first-request startup work for warmed worker and process executors.
+
+`WorkerExecutor` now also uses a CPU-aware default pooled `maxSize`, capped at `4`, instead of always defaulting to a single worker shell.

.prettierignore

@@ -1,4 +1,6 @@
 .worktrees
+docs/.vitepress/cache
+docs/.vitepress/dist
 node_modules
 package-lock.json
 packages/**/dist