fix(test): set --max-old-space-size=6144 on test:coverage to prevent OOM under --runInBand (#3554)

`test:coverage` runs `jest --runInBand` (single Node process) so
`workerIdleMemoryLimit` from #3550 does not apply — there are no worker
children to recycle. Without an explicit heap cap, Node defaults to ~2 GB
old-space which is enough for devkit (~18 suites) but immediately OOMs on
larger downstream test suites (trawl_node hit OOM at 1.9 GB on 214 suites).

Setting `--max-old-space-size=6144` matches the existing per-project
override that downstream projects had to maintain locally as patches.
Bumping it upstream eliminates the divergence and prevents the
`feedback_update_stack_theirs_wipes_patches` failure mode where
`/update-stack --theirs` silently strips the override.

Sized for the largest known downstream (trawl_node ~214 suites peaks ~4.3 GB
pre-fixes / ~2 GB post). Headroom keeps room for further growth without
re-tuning. CI runners on lily ARC have ≥6 GiB, GitHub-hosted runners have
7 GiB — both fit.

Note: `workerIdleMemoryLimit: '512MB'` from #3550 still applies for non-
coverage parallel runs (`test:parallel-smoke`, etc.) where worker children
exist.

Author: PierreBrisorgueil

package.json

@@ -34,7 +34,7 @@
     "test:integration": "cross-env NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --runInBand --testPathPatterns='integration'",
     "test:e2e": "cross-env NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --runInBand --testPathPatterns='e2e'",
     "test:watch": "cross-env NODE_ENV=test NODE_OPTIONS=--experimental-vm-modules jest --watchAll",
-    "test:coverage": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --expose-gc\" jest --coverage --runInBand",
+    "test:coverage": "cross-env NODE_ENV=test NODE_OPTIONS=\"--experimental-vm-modules --max-old-space-size=6144 --expose-gc\" jest --coverage --runInBand",
     "test:parallel-smoke": "cross-env NODE_ENV=test node scripts/parallel-integration.smoke.js",
     "lint": "eslint ./modules ./lib ./config ./scripts",
     "seed:dev": "cross-env NODE_ENV=development node scripts/seed.js seed",