test(sandbox): give the probe-timeout test headroom over vitest's default

`bounds the default probes` runs a real launcher that sleeps 1s under the
5000ms default probe budget, all wrapped in vitest's 5000ms default test
timeout. The blocking spawnSync races that wrapper and tips over under the
load spike of a full parallel run — a pre-existing, load-sensitive flake
(noted as unrelated in this PR's original description). Give the test an
explicit 20s timeout so its bounded subprocess work never races the default.

packages/sandbox/sandbox-local/tests/local.spec.ts

@@ -339,7 +339,10 @@ describe('probeTimeoutMs config', () => {
       { platform: 'linux', probeBwrap: () => false, landlockLauncher: launcher },
     )
     expect(() => impatient.sandbox.confine(['true'], RO)).toThrow(expect.objectContaining({ code: SANDBOX_UNAVAILABLE }))
-  })
+    // The patient probe blocks on a real 1s launcher under the 5000ms default
+    // budget; an explicit timeout keeps the test clear of vitest's 5000ms
+    // default, which the blocking spawnSync would otherwise race under load.
+  }, 20_000)
 })
 
 describe('the default seatbelt probe (sandbox-exec contract)', () => {