feat(taskctl): show structured error history in taskctl inspect #272

Task Description

When a task fails or is retried, taskctl inspect only shows the current state and comments. There's no structured history of what went wrong on prior attempts — making debugging and steering decisions difficult for the PM.

Implementation

• Add error_history array to pipeline state: { attempt, stage, reason, timestamp }[]
• Populate on: timeout, resurrection, adversarial ISSUES_FOUND/CRITICAL_ISSUES_FOUND, max retries exceeded
• Surface in taskctl inspect output under a clear 'Retry History' section

Quality Gates (Non-Negotiable)

• TDD: Write tests before implementation
• Linting passes
• Local verification: all tests pass

Acceptance Criteria

• Failed attempts recorded with stage, reason, and timestamp
• taskctl inspect shows full retry history
• Existing tasks with no error history show nothing (backward compatible)