test: enable vmForks for targeted channel test runs

Channel tests were always using process forks, missing the shared
transform cache that vmForks provides. This caused ~138s import
overhead per file. Now uses vmForks when available, matching the
pattern already used by unit-fast and extensions suites.

scripts/test-parallel.mjs

@@ -487,7 +487,7 @@ const createTargetedEntry = (owner, isolated, filters) => {
         "run",
         "--config",
         "vitest.channels.config.ts",
-        ...(forceForks ? ["--pool=forks"] : []),
+        ...(forceForks ? ["--pool=forks"] : useVmForks ? ["--pool=vmForks"] : []),
         ...filters,
       ],
     };