fix(image): match Next.js 16 default image sizes

[NathanDrake2406]

Summary

• Match Next.js 16's default images.imageSizes by removing 16
• Reuse the shared server default when generating client image config
• Keep explicit imageSizes configurations containing 16 supported

Why

vinext is pinned to Next.js 16.2.7, but still used the pre-v16 default:

[16, 32, 48, 64, 96, 128, 256, 384]

Next.js 16 removed 16 because it is rarely requested and adds an unnecessary
candidate to responsive srcset output. The mismatch also meant vinext's image
optimizer accepted a default width that Next.js 16 no longer accepts.

Behavior

Scenario	Before	After
Default 16px fixed image	Emits 16px and 32px candidates	Both targets snap to one 32px candidate
Default optimizer request for w=16	Accepted	Rejected
Explicit images.imageSizes containing 16	Accepted	Unchanged

Validation

• vp test run tests/image-component.test.ts tests/shims.test.ts
  • 1,322 tests passed
• vp check packages/vinext/src/config/next-config.ts packages/vinext/src/index.ts packages/vinext/src/server/image-optimization.ts packages/vinext/src/shims/image.tsx tests/image-component.test.ts tests/shims.test.ts
  • Formatting, lint, and types passed for all six files
• node scripts/check-shim-types.mjs
  • 24 public shim modules matched their vendored types
• Pre-commit full check, staged tests, and knip passed

Risk

This is an intentional Next.js 16 compatibility change for projects that rely
on the default image sizes. Projects that still require 16px optimization can
opt back in with images.imageSizes, matching Next.js's migration guidance.
Explicit configurations are otherwise unchanged.

References

• Next.js 16 image config default
• Next.js 16 upgrade guidance
• vinext PR #2700 parity-gap note

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@2704

npm i https://pkg.pr.new/create-vinext-app@2704

npm i https://pkg.pr.new/@vinext/types@2704

npm i https://pkg.pr.new/vinext@2704

commit: 6344808

[github-actions]

Performance benchmarks

Compared 6344808 against base 05eee9f using alternating same-runner rounds. Next.js was unchanged and skipped.

0 improved · 0 regressed · 6 within ±1.5%

Scenario	Framework	Baseline	Current	Change
Client bundle size (gzip)	vinext	132.4 KB	132.4 KB	⚫ +0.0%
Client entry size (gzip)	vinext	119.7 KB	119.7 KB	⚫ +0.0%
Dev server cold start	vinext	2.84 s	2.83 s	⚫ -0.5%
Production build time	vinext	3.13 s	3.13 s	⚫ +0.1%
RSC entry closure size (gzip)	vinext	103.3 KB	103.3 KB	⚫ +0.0%
Server bundle size (gzip)	vinext	177.8 KB	177.8 KB	⚫ -0.0%

View detailed results and traces

_{🟢 improvement · 🔴 regression · ⚫ change below 1.5% · paired base/head}