revert: Make n8n-workflow a peer dependency in ai-utilities

[DawidMyslak]

Summary

Reverts #26404. Moving n8n-workflow from dependencies to peerDependencies in @n8n/ai-utilities broke the monorepo build — peer deps aren't automatically resolved for the package itself during build, so ai-utilities can no longer find n8n-workflow.

The proper fix needs n8n-workflow in both devDependencies (for monorepo build) and peerDependencies (for npm consumers). Will follow up with a corrected PR.

Related Linear tickets, Github issues, and Community forum posts

https://linear.app/n8n/issue/NODE-4532

Review / Merge checklist

• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.
• PR Labeled with release/backport (if the PR is an urgent fix that needs to be backported)

[cubic-dev-ai]

No issues found across 2 files

Architecture diagram

sequenceDiagram
    participant Build as Build System (Monorepo)
    participant AI as @n8n/ai-utilities
    participant WF as n8n-workflow
    participant Run as n8n Runtime

    Note over Build, WF: Build-time Resolution (Restored)
    Build->>AI: Start build/transpilation
    AI->>Build: Resolve module "n8n-workflow"
    
    alt Dependency Found
        Build->>WF: CHANGED: Locate via "dependencies" (workspace:*)
        WF-->>AI: Provide type definitions & source
        AI-->>Build: Compilation success
    else Peer Dependency Error (Reverted State)
        Build--xAI: Fails to resolve (Peer deps not auto-linked in build)
    end

    Note over AI, Run: Runtime Control Flow
    Run->>AI: Call AI utility function
    AI->>WF: Access shared workflow primitives (Interfaces/Classes)
    WF-->>AI: Context/Data
    AI-->>Run: Return AI process result

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[blacksmith-sh]

Found 1 test failure on Blacksmith runners:

Failure

Test	View Logs
tests/e2e/workflows/editor/canvas/canvas-nodes.spec.ts/ Canvas Node Manipulation and Navigation › should add switch node and test connections	View Logs