Parallelize managed unit precompile

docs/wasm-runtime-architecture.md

@@ -238,7 +238,12 @@ is the runtime core ABI. Old and new service binaries therefore never publish
 or read the same unit path during an ABI transition. The managed restart builds
 and serializes the complete next generation before stopping the old service;
 failure aborts the switch and leaves the running generation intact. Old
-generation directories are retained as an explicit rollback path.
+generation directories are retained as an explicit rollback path. Two
+low-priority precompile processes are used by default so independent units do
+not serialize deployment time while live workers retain scheduler priority.
+`PRECOMPILE_JOBS` or `UCE_PRECOMPILE_JOBS` may select 1–16 processes. Unit
+publication and the shared generation PCH use separate advisory locks, and any
+worker/reporting failure rejects the candidate generation.
 
 The proactive compiler and request workers coordinate through per-unit file
 locks and a lock-protected demand-priority queue under `BIN_DIRECTORY`. A small