fix: restore 8 KiB Node buffer pool on linux (#326334)

Node 24.18 changed Buffer.poolSize from 8 KiB to 64 KiB in
https://github.com/nodejs/node/commit/d3ef4122eefb6b293b72b348fc6ea4cb602622a5

Node uses the pool for Buffer allocations smaller than half the pool size.
As a result, allocations below 32 KiB can now be views into a shared 64 KiB
backing ArrayBuffer.

VS Code's VSBuffer preserves these pooled backing stores. Webview resource
streaming then forwards Uint8Array views through transferable streams without
copying just the visible byte range. Structured clone consequently serializes
the full 64 KiB backing store.

Chromium's mojo_base::BigBuffer has a 64 KiB inline limit. The structured-clone
envelope makes these payloads just above that limit, so
each message switches from inline storage to writable shared memory.

On POSIX, each writable shared-memory region carries two file descriptors: its
writable descriptor and a read-only descriptor used for conversion. Under a
renderer RLIMIT_NOFILE of 1024, a burst of webview resource messages therefore
consumes two descriptors per chunk.

Instrumentation of VS Code loading the Codex webview showed:

- 1,910 large CommonCloneableMessage serializations;
- the dominant payload sizes were 65,556 and 65,557 bytes;
- renderer descriptors increasing through 1021, 1022, and 1023;
- recvmsg() returning message bytes with MSG_CTRUNC once descriptors could no
  longer be installed;
- Mojo buffering messages with missing handles;
- subsequent resource failures and service-worker Cache.put() network errors.

Restoring the previous 8 KiB pool size prevents small VS Code buffers from
retaining 64 KiB backing stores. Their structured-clone messages remain below
BigBuffer's inline threshold and no longer require shared-memory descriptor
pairs.

Instrumentation with this override removed the 65,556/65,557-byte message
burst and avoided the original stale-FD reassociation and clean renderer exit.
Larger shared-memory messages can still exhaust descriptors under sufficiently
heavy pressure, so this is a targeted mitigation rather than a replacement for
the Mojo MSG_CTRUNC fix.
Node's default pool size.

src/bootstrap-node.ts

@@ -5,12 +5,18 @@
 
 import * as path from 'node:path';
 import * as fs from 'node:fs';
+import { Buffer } from 'node:buffer';
 import { createRequire } from 'node:module';
 import type { IProductConfiguration } from './vs/base/common/product.js';
 
 const require = createRequire(import.meta.url);
 const isWindows = process.platform === 'win32';
 
+// Avoid 64 KiB pooled backing stores crossing Mojo's shared-memory threshold.
+if (process.platform === 'linux') {
+	Buffer.poolSize = 8 * 1024;
+}
+
 // increase number of stack frames(from 10, https://github.com/v8/v8/wiki/Stack-Trace-API)
 Error.stackTraceLimit = 100;