Fix/add instrumentation to next build

[NathanColosimo]

Fixes #1845

This fixes a discovery gap in @workflow/next by including Next server instrumentation entrypoints in workflow discovery.

• adds support for workflows imported only from instrumentation.ts and src/instrumentation.ts
• adds a regression test covering instrumentation-only manifest inclusion in the Next workbenches.
• Porting over these changes also fixes my local project where I was getting this issue when using a bun patchfile

*lmk if you think there are other files that should be added here

[changeset-bot]

🦋 Changeset detected

Latest commit: 202defd

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 17 packages

Name	Type
@workflow/next	Patch
workflow	Patch
@workflow/ai	Patch
@workflow/world-testing	Patch
@workflow/core	Patch
@workflow/builders	Patch
@workflow/cli	Patch
@workflow/nitro	Patch
@workflow/vitest	Patch
@workflow/web-shared	Patch
@workflow/web	Patch
@workflow/astro	Patch
@workflow/nest	Patch
@workflow/rollup	Patch
@workflow/sveltekit	Patch
@workflow/vite	Patch
@workflow/nuxt	Patch

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