fix(engine): respect cgroup memory limits in low-memory detection (#1373)

getSystemTotalMb returned os.totalmem() — the host's physical RAM — so a
4GB Docker container on a 32GB host never auto-flagged as low-memory and
the low-memory render profile didn't activate exactly where it's needed
most. Read the cgroup v2 limit (/sys/fs/cgroup/memory.max, with the v1
fallback and its no-limit sentinel handled) and use min(host, cgroup).
The probe is best-effort and non-Linux platforms never touch /sys.

Review follow-ups: worker sizing (calculateOptimalWorkers) and the
getSystemResources diagnostics previously read os.totalmem() directly
and now use getSystemTotalMb(), so container limits actually govern
parallel spawn decisions; CLI telemetry reports the effective total as
well. The cgroup probe result is cached for the process lifetime (the
limit is immutable per process) with a test reset hook; a detected limit
logs once so operators can see which source governs, and a
present-but-unreadable cgroup file warns once instead of failing
silently — absence stays silent. The root-path-vs-/proc/self/cgroup
trade-off is documented at the path constants. cli/tsconfig.json gains
the gcp-cloud-run/sdk source alias (matching the existing producer and
aws-lambda entries) so the cli typecheck resolves from source in a
fresh checkout.

Refs #1193, #1194, #1195, #1236

packages/engine/src/services/parallelCoordinator.ts

@@ -5,7 +5,7 @@
  * Auto-detects optimal worker count based on CPU/memory.
  */
 
-import { cpus, freemem, totalmem } from "os";
+import { cpus, freemem } from "os";
 import { existsSync, mkdirSync, readdirSync } from "fs";
 import { copyFile, rename } from "fs/promises";
 import { join } from "path";
@@ -26,6 +26,7 @@ import { DEFAULT_CONFIG, type EngineConfig } from "../config.js";
 import { assertSwiftShader } from "../utils/assertSwiftShader.js";
 import { readWebGlVendorInfoFromCanvas } from "../utils/readWebGlVendorInfoFromCanvas.js";
 import { resolveHeadlessShellPath } from "./browserManager.js";
+import { getSystemTotalMb } from "./systemMemory.js";
 
 export interface WorkerTask {
   workerId: number;
@@ -153,7 +154,7 @@ export function calculateOptimalWorkers(
   // Use total memory instead of free memory — macOS reports misleadingly low
   // freemem() because it aggressively caches files in "inactive" memory that
   // is immediately reclaimable.
-  const totalMemoryMB = Math.round(totalmem() / (1024 * 1024));
+  const totalMemoryMB = getSystemTotalMb();
   const memoryBasedWorkers = Math.max(1, Math.floor((totalMemoryMB * 0.5) / MEMORY_PER_WORKER_MB));
 
   const frameBasedWorkers = Math.floor(totalFrames / MIN_FRAMES_PER_WORKER);
@@ -429,7 +430,7 @@ export function getSystemResources(): {
 } {
   return {
     cpuCores: cpus().length,
-    totalMemoryMB: Math.round(totalmem() / (1024 * 1024)),
+    totalMemoryMB: getSystemTotalMb(),
     freeMemoryMB: Math.round(freemem() / (1024 * 1024)),
     recommendedWorkers: calculateOptimalWorkers(1000),
   };