fix(core): Reduce planner workflow bias and fix data-table task routing (no-changelog)

[OlegIvaniv]

Summary

• Planner now uses data-table kind for all table operations (create, delete, modify) instead of falling back to delegate with incomplete tools
• Made blueprint data-table columns optional to support non-creation operations
• Updated accumulator to derive task title/spec from purpose when columns absent
• Added scope boundary to data-table agent to prevent cross-task side effects
• Orchestrator now handles single remaining tasks directly on replan instead of always creating a new plan via create-tasks
• Added standalone data-table operations section to best-practices guide

Related Linear tickets, Github issues, and Community forum posts

Review / Merge checklist

• I have seen this code, I have run this code, and I take responsibility for this code.
• PR title and summary are descriptive. (conventions)
• Docs updated or follow-up ticket created.
• Tests included.
• PR Labeled with Backport to Beta, Backport to Stable, or Backport to v1 (if the PR is an urgent fix that needs to be backported)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[cubic-dev-ai]

No issues found across 7 files

Architecture diagram

sequenceDiagram
    participant User
    participant Orch as Orchestrator (System Prompt)
    participant Planner as Plan Agent
    participant Accum as Blueprint Accumulator
    participant DTAgent as Data Table Agent
    participant Tool as Specialized Tools (Workflow/DT/Delegate)

    Note over User,Tool: Planning Phase (Initial Request)

    User->>Orch: Request table/workflow operations
    Orch->>Planner: Identify tasks & design blueprint
    
    loop For each task
        Planner->>Planner: CHANGED: Use 'data-table' kind for ALL table ops<br/>(Create, Delete, Modify, Seed)
        Planner->>Accum: NEW: add-plan-item (Columns optional)
        Accum->>Accum: NEW: Derive task spec from 'purpose'<br/>if columns are absent
    end

    Planner-->>Orch: Submit Plan
    Orch->>Orch: Schedule tasks

    Note over Orch,DTAgent: Execution Phase

    Orch->>DTAgent: Execute Data Table task
    DTAgent->>DTAgent: NEW: Enforce scope boundary<br/>(Ignore context from other tasks)
    opt Task includes seed data
        DTAgent->>DTAgent: NEW: Create table THEN insert rows
    end
    DTAgent-->>Orch: Task Result (Success/Failure)

    Note over Orch,Tool: Recovery Phase (on Failure)

    alt Task Failed: Replan needed
        Orch->>Orch: Inspect failure & remaining work
        
        alt NEW: Only 1 simple task remains
            Orch->>Tool: Call specific agent tool directly<br/>(e.g., manage-data-tables-with-agent)
            Tool-->>User: Final Result
        else Multiple tasks or complex dependencies
            Orch->>Planner: Call 'create-tasks' for full replan
            Planner-->>User: New Plan Visibility
        end
    end

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[Cadiac]

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