[ENHANCEMENT] Show $.$$ API cost tally of Parent task (full orchestration) above $.$$ cost tally of current worker task

[ScotterMonk]

Problem (one or two sentences)

Right now I see only one API cost tally at a time and it is for current model.
If I have an orchestration going on, I'd like to see a tally at the top for all workers (orchestrator, code, etc.) involved in the current overall task, not just seeing orchestrator cost-so-far by itself and various worker threads as they are spawned for one task, run up a fee, and then the fee disappears from view.

Context (who is affected and when)

See "Problem" above.

Desired behavior (conceptual, not technical)

See "Problem" above.

Constraints / preferences (optional)

See "Problem" above.

Request checklist

• I've searched existing Issues and Discussions for duplicates
• This describes a specific problem with clear context and impact

Roo Code Task Links (optional)

No response

Acceptance criteria (optional)

No response

Proposed approach (optional)

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Trade-offs / risks (optional)

No response

[roomote-v0]

I've analyzed this issue and here's my proposed implementation plan:

Problem

Currently, when viewing a subtask (e.g. a worker spawned by an orchestrator), the TaskHeader only shows that subtask's own cost. Users want to see the parent/root orchestration's total accumulated cost (across all workers) when viewing any subtask.

Current Architecture

• HistoryItem already tracks rootTaskId, parentTaskId, and childIds
• aggregateTaskCostsRecursive() in src/core/webview/aggregateTaskCosts.ts already recursively sums costs for a task and all its children
• TaskHeader already supports aggregatedCost display (with asterisk) for tasks that have subtasks
• The getTaskWithAggregatedCosts message handler already computes aggregated costs for a given task ID
• currentTaskItem exposes parentTaskId and rootTaskId to the webview

Proposed Approach

When viewing a subtask, fetch and display the root/parent orchestration's aggregated cost above the current worker's cost.

1. ChatView: Request root task aggregated costs for subtasks (webview-ui/src/components/chat/ChatView.tsx)

• In the existing useEffect that requests aggregated costs (line ~500), add a branch: if the current task has a rootTaskId (or parentTaskId as fallback), also request getTaskWithAggregatedCosts for the root task ID.
• The response will be stored in the existing aggregatedCostsMap keyed by the root task ID.

2. Pass root orchestration cost to TaskHeader (webview-ui/src/components/chat/ChatView.tsx)

• Add a new prop rootOrchestrationCost (or similar) to TaskHeader, computed by looking up currentTaskItem.rootTaskId in aggregatedCostsMap.
• Only pass this when currentTaskItem.parentTaskId exists (i.e., we're viewing a subtask).

3. Display root orchestration cost in TaskHeader (webview-ui/src/components/chat/TaskHeader.tsx)

• Add a new optional prop rootOrchestrationCost?: number to TaskHeaderProps.
• When this prop is present and > 0, render a line above the current task's cost showing something like "Orchestration total: $X.XX" with appropriate styling and a tooltip explaining it includes all workers in the orchestration.
• Use existing i18n patterns for the label (add new translation keys like chat:costs.orchestrationTotal).

4. Add translation keys (locales/)

• Add chat:costs.orchestrationTotal (e.g., "Full orchestration: ${{cost}}") and a tooltip key like chat:costs.orchestrationTotalTooltip (e.g., "Total cost across all tasks in this orchestration").

5. Tests

• Update TaskHeader.spec.tsx to verify the root orchestration cost renders when provided
• Update ChatView tests if needed for the new useEffect branch
• Ensure existing aggregateTaskCosts.spec.ts tests still pass

Summary

This approach is minimal and leverages the existing aggregated cost infrastructure. The key insight is that rootTaskId is already tracked on every subtask, so we just need to request aggregated costs for the root task and pipe it into the header. No backend changes needed beyond what's already there.

Please mention @roomote in a comment saying that you approve this plan, and I'll proceed with the implementation.