docs: update memory leak debugging skill

[mturac]

Summary

• Update the memory leak debugging skill to prefer the built-in heap snapshot tools.
• Add guidance for comparing snapshots, inspecting retainers, and closing loaded snapshots.
• Keep memlab and the fallback comparison script as external fallback paths.

Issue #2329.

Validation

• git diff --check origin/main...HEAD
• npm run check-format

[mturac]

Validation refreshed on the current head 709080ad39547376e8ac1bffe6f95dbdb042c060.

Local validation:

git diff --check origin/main...HEAD
npm run check-format
npm run build

All pass locally. The current GitHub checks are also green across the visible Node 22/24/26 test matrix on macOS, Ubuntu, and Windows, plus the required format, docs, title, check-changes, and CLA checks.

[mturac]

Rebased this branch onto the current main in d36463da312f.

Validation on the rebased head:

git diff --check origin/main...HEAD
npm run check-format
npm run test -- --test-concurrency=1 --retry

All pass locally.

[Lightning00Blade]

Thanks for the PR!
FYI changed the closes to issue, so we keep it open while we do other changes as well.

[mturac]

The current head is approved and locally validated, but the required Compile and run tests and Check code before submitting workflows are both in action_required and need maintainer approval to start.

Could a maintainer approve those workflow runs when convenient? There are no additional code changes pending on the branch.