Add universal noise and optional denoiser noise inputs

[JPPhoto]

Summary

Adds a new Universal Noise invocation for architecture-specific latent noise generation and extends supported denoise invocations to accept optional external noise inputs while preserving existing behavior when noise is not connected. This backwards compatibility means that existing workflows, including those generated by the canvas and linear frontend, continue to work without modification because all new noise inputs are optional and default to the existing internal noise-generation path.

Backend changes cover FLUX, FLUX.2, SD3, CogView4, Z-Image, and Anima denoisers, plus focused validation and regression tests. Frontend-facing schema was regenerated so the new invocation and denoise noise inputs are available in invokeai/frontend/web/src/services/api/schema.ts. Documentation was updated in invokeai/docs/contributing/NEW_MODEL_INTEGRATION.md to require extending Universal Noise when possible for new architectures that support external noise.

Also added inline denoiser documentation for the existing img2img scheduler-parity limitations, wrote tests for these limitations, and preserved explicit regression coverage by marking the known scheduler-mismatch cases as expected failures rather than dropping those tests.

Related Issues / Discussions

QA Instructions

Try different models using the new Universal Noise node as noise input. Verify that it works with different start points and existing input latents whether using the added noise or leaving it off.

Merge Plan

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• ❗Changes to a redux slice have a corresponding migration
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)