Type process.getBuiltinModule results as module namespaces

Under @types/node, process.getBuiltinModule("node:os") types as the
module namespace, which lowered as an unchecked dynamic value and failed.
A string-literal id naming a supported builtin now lowers to the namespace
value an `import * as` binding has, including pi's cast-and-probe spelling
`(process as P).getBuiltinModule?.("node:os") ?? null`; a nullable
namespace binding narrowed present keys the same member tables, and a
namespace is truthy. process.features read as a whole value (`"sea" in
process.features`) is an object holding none of the flags, matching the
existing member reads.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/corpus/6232-process-builtin-module-typed/main.ts

@@ -0,0 +1,28 @@
+// process.getBuiltinModule and process.features under @types/node: a
+// literal id types as the module namespace, so the result is the same
+// object `import * as os` binds (pi's user-agent probe casts process and
+// calls the member optionally), and process.features is an object a
+// feature probe can test with `in` (pi's single-executable check).
+import * as os from "node:os";
+import type * as NodeOs from "node:os";
+
+const direct = process.getBuiltinModule("node:os");
+console.log("direct", direct.platform() === os.platform(), direct.EOL === os.EOL);
+console.log("bare id", process.getBuiltinModule("os").arch() === os.arch());
+
+type ProcessWithOsBuiltinModule = typeof process & {
+  getBuiltinModule?: (id: "node:os") => typeof NodeOs;
+};
+function loadNodeOs(): typeof NodeOs | null {
+  if (typeof process === "undefined" || !(process.versions?.node || process.versions?.bun)) {
+    return null;
+  }
+  return (process as ProcessWithOsBuiltinModule).getBuiltinModule?.("node:os") ?? null;
+}
+const nodeOs = loadNodeOs();
+const agent = nodeOs ? `pi (${nodeOs.platform()} ${nodeOs.release()}; ${nodeOs.arch()})` : "pi (browser)";
+console.log("agent", agent === `pi (${os.platform()} ${os.release()}; ${os.arch()})`);
+console.log("present", nodeOs !== null, nodeOs ? typeof nodeOs.homedir() : "none");
+
+const isNodeSeaBinary = "sea" in process.features && process.features.sea === true;
+console.log("sea", isNodeSeaBinary, "sea" in process.features);

tests/corpus/6232-process-builtin-module-typed/package.json

@@ -0,0 +1 @@
+{ "type": "module" }

tests/corpus/6232-process-builtin-module-typed/tsconfig.json

@@ -0,0 +1,7 @@
+{
+  "compilerOptions": {
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "strict": true
+  }
+}