feat: implement bi-directional Linear/Jira integration

[echobt]

Summary

This PR implements the AGENT 5 mission for Linear and Jira integration with full bi-directional sync capabilities for the Cortex CLI.

Changes

Linear Client Enhancements (cortex-engine/src/linear/)

• Added URL and short reference parsing with regex patterns (e.g., LIN-123, https://linear.app/team/issue/LIN-123)
• Implemented retry logic with exponential backoff (3 retries, 100ms initial delay)
• Added write operations:
  • create_issue() - Create new issues with full field support
  • add_comment() - Add comments to issues
  • update_issue_state() - Change issue status
  • update_issue_priority() - Change issue priority
  • update_issue_assignee() - Assign/unassign users
• Added enrich_context() method for automatic ticket detail enrichment
• Added LinearRef type for extracted references
• Added CreateIssueInput type for issue creation
• Comprehensive test coverage (10 tests)

New Jira Client (cortex-engine/src/jira/)

• Complete REST API client supporting both Jira Cloud and Server/Data Center
• URL parsing for:
  • Cloud: https://company.atlassian.net/browse/PROJ-123
  • Server: https://jira.company.com/browse/PROJ-123
• Rate limiting (500 requests per 5 minutes for Jira Cloud)
• Retry logic with exponential backoff for transient failures
• Full CRUD operations:
  • get_issue() / get_issue_details() - Fetch issue information
  • create_issue() - Create new issues
  • update_issue() - Update issue fields
  • add_comment() - Add comments
• Workflow operations:
  • get_transitions() - List available transitions
  • transition_issue() - Change issue status
• assign_issue() - Assign/unassign users
• search_issues() - JQL query support
• ADF (Atlassian Document Format) text extraction
• enrich_context() for automatic ticket detail enrichment
• Comprehensive test coverage (9 tests)

Module Integration

• Added jira module to cortex-engine/src/lib.rs
• Added comprehensive re-exports for both Linear and Jira types

Testing

• All 19 unit tests pass (10 Linear + 9 Jira)
• cargo check passes
• cargo fmt applied

Related

Resolves: ORCHESTRATE/AGENT_5_LINEAR_JIRA.md