perf(wsl): pooled wsl.exe command loops and orcad compile cache on the WSL wake path (C4 follow-up) (#27923)

* perf(wsl): run stdin-free probes over pooled wsl.exe command loops; cache orcad's compiled bundle

The WSL wake path made ~37 sequential wsl.exe starts at ~180 ms each. Stdin-free
execCommand calls now go through a few long-lived wsl.exe sh loops (one command at a
time per loop, own session, stdin at EOF, base64-framed output). SSH has no such
method, so its commands and options are unchanged.

orcad enables Node's compile cache inside a client-managed slot, and hands it to the
profile preflight child, which compiles the same bundle.

* fix(orcad): share the slot compile cache with the preflight only in a managed slot

An unmanaged orcad started with its own NODE_COMPILE_CACHE kept that
location for its preflight before; never redirect it into the install dir.

src/shared/orcad-idle-exit.ts

@@ -4,12 +4,7 @@
  */
 import { z } from 'zod'
 
-/**
- * Set only by a client's managed launch. Enables idle exit and names the host's activation
- * fence, so an update or rollback in flight keeps the server up. User-started servers never
- * carry it.
- */
-export const ORCAD_MANAGED_ACTIVATION_ROOT_ENV = 'ORCA_ORCAD_MANAGED_ACTIVATION_ROOT'
+export { ORCAD_MANAGED_ACTIVATION_ROOT_ENV } from './orcad-managed-launch-env'
 /** Test-only quiet period; a client forwards it to the servers it launches. */
 export const ORCAD_E2E_IDLE_TIMEOUT_ENV = 'ORCA_E2E_ORCAD_IDLE_TIMEOUT_MS'
 export const ORCAD_IDLE_EXIT_TIMEOUT_MS = 15 * 60_000

src/shared/orcad-managed-launch-env.ts

@@ -0,0 +1,6 @@
+/**
+ * Set only by a client's managed launch. Enables idle exit and names the host's activation
+ * fence, so an update or rollback in flight keeps the server up. User-started servers never
+ * carry it. Dependency-free so the orcad launcher can read it.
+ */
+export const ORCAD_MANAGED_ACTIVATION_ROOT_ENV = 'ORCA_ORCAD_MANAGED_ACTIVATION_ROOT'