perf(dev): bound light webpack runtime

[beruro]

Problem

The light development webpack mode still enables browser-client runtime features and cache behavior that retain unnecessary memory during local development.

Solution

• Disable browser-client runtime features in light development mode.
• Keep development caching memory-only and bounded to one generation.
• Preserve isolated production filesystem caching.
• Validation: 5 Node regression tests and performance-lifecycle review.

Potential risks

• Development rebuild speed may trade off against lower retained memory.
• Production cache behavior must remain isolated from the light-development override.
• Memory improvement should be verified with a real development-session measurement, not inferred from configuration alone.