fix: comprehensive orchestrator mode restoration for sub-tasks (#5747)

[roomote]

This PR fixes the orchestrator mode restoration issue described in #5747 where sub-tasks launched by the Orchestrator mode were not properly returning to the parent Orchestrator task after completion or interruption.

Problem

• When sub-tasks get interrupted (e.g., Claude "overloaded" error), the main task doesn't return to orchestrator mode
• Modes like "architect" and "ask" have lower success rates of returning to parent tasks after completion
• Users expect to be able to close VSCode, reopen it, and restart with the Orchestrator top-level task

Solution

This PR implements a comprehensive fix with four major components:

1. Enhanced mode restoration in resumePausedTask method

• Added comprehensive mode restoration logic in Task.ts lines 766-793
• Checks if current mode differs from paused mode and restores it with proper error handling and logging

2. Mode restoration safety net in finishSubTask method

• Enhanced ClineProvider.ts lines 229-264 to include mode restoration as a safety net
• Ensures parent task's mode is properly restored regardless of how the sub-task ends

3. Mode validation and restoration in task resumption from history

• Added mode restoration logic in Task.ts lines 814-838
• Ensures correct mode is restored when tasks are resumed from history

4. Error handling for interrupted sub-tasks

• Enhanced error handling in Task.ts lines 1462-1520 to include mode restoration
• Ensures parent task mode is restored even during error scenarios

Key Changes

• src/core/task/Task.ts: Enhanced resumePausedTask(), resumeTaskFromHistory(), and stream error handling methods with comprehensive mode restoration logic
• src/core/webview/ClineProvider.ts: Added mode restoration safety net in finishSubTask() method

Testing

• All existing tests pass
• The fix provides comprehensive mode restoration coverage across all sub-task lifecycle scenarios
• Handles normal completion, interruption, error handling, and task resumption from history

Impact

• Fixes the core issue where orchestrator mode wasn't properly restored after sub-task completion/interruption
• Improves reliability of the orchestrator workflow
• Ensures consistent user experience when resuming tasks from history

Fixes #5747

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Important

Fixes orchestrator mode restoration for sub-tasks, ensuring correct mode restoration on task resumption, completion, and interruption.

• Behavior:
  • Fixes orchestrator mode restoration for sub-tasks in Task.ts and ClineProvider.ts.
  • Ensures mode restoration on task resumption, completion, and interruption.
• Functions:
  • resumePausedTask() and resumeTaskFromHistory() in Task.ts now include mode restoration logic.
  • finishSubTask() in ClineProvider.ts adds a safety net for mode restoration.
  • Enhanced error handling in Task.ts to restore mode during sub-task interruptions.
• Testing:
  • All existing tests pass, ensuring comprehensive mode restoration coverage across scenarios.
• Impact:
  • Resolves issue Sub-tasks not returning to Orchestrator, re-starting tasks not working #5747, improving orchestrator workflow reliability and user experience.

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[ellipsis-dev]

The mode restoration logic in resumePausedTask (and similarly in resumeTaskFromHistory and in the streaming error handling block) is very similar. Consider extracting this logic into a dedicated helper function to reduce duplication and simplify maintenance.