Add mcp-server subcommand for MCP protocol integration

[Copilot]

Summary

Successfully implemented the "mcp-server" sub-command that uses github.com/mark3labs/mcp-go/mcp.

Changes

• Add github.com/mark3labs/mcp-go dependency to go.mod
• Create internal/mcp package for MCP server implementation
• Implement MCP tools for JIRA operations (get-issue, update-issue-status, add-comment, get-comments, create-issue)
• Add "mcp-server" sub-command to main.go that starts the MCP server via stdio
• Test the implementation manually
• Update README with mcp-server documentation
• Code review completed
• Security scan completed (no vulnerabilities found)
• Refactor to follow slack-cli pattern (simpler structure, better docs)

MCP Tools Implemented

1. get_issue - Get details of a JIRA issue
2. update_issue_status - Update the status of a JIRA issue
3. add_comment - Add a comment to a JIRA issue
4. get_comments - Get comments on a JIRA issue
5. create_issue - Create a new JIRA issue

Improvements Applied from slack-cli PR #6

• Moved MCP code from internal/mcp/ to mcp.go at root (simpler file structure)
• Moved tests from internal/mcp/server_test.go to mcp_test.go at root
• Improved README documentation structure with separate "Direct CLI Usage" and "MCP Server Mode" sections
• Added detailed setup instructions and example usage
• Better organized tool descriptions

Security Summary

No vulnerabilities found during CodeQL security analysis.

Original prompt

Add an "mcp-server" sub-command that uses github.com/mark3labs/mcp-go/mcp.

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[alexec]

@copilot look at kitproj/slack-cli#6 and think if we should copy some of those ideas.

[Copilot]

@copilot look at kitproj/slack-cli#6 and think if we should copy some of those ideas.

Applied the following improvements from slack-cli PR #6 in commit 523e9a0:

• Moved MCP code from internal/mcp/ to mcp.go at root (simpler 67-line file structure like slack-cli)
• Moved tests to mcp_test.go at root
• Improved README structure with separate "Direct CLI Usage" and "MCP Server Mode" sections
• Added detailed setup instructions and example usage pattern
• Better tool descriptions following the slack-cli example