Add e-signature plugin with Signeasy MCP integration

[rondavid-n]

Summary

1. Added new esignature plugin for managing e-signature workflows via MCP
2. Integrated e-signature capabilities into the legal plugin for contract signing workflows

E-signature Plugin
New plugin providing comprehensive e-signature management:
Commands:

1. /signature-status - Dashboard view of pending documents, completion rates, and account info
2. /document-search - Search documents by name across pending and signed
3. /send-reminder - Send reminder emails to pending signers
4. /document-details - Get comprehensive info about any document with signer status
5. /cancel-request - Safely cancel/void pending signature requests

Skills:

1. document-tracking - Track document lifecycle, monitor pending requests, follow up on stale documents
2. signature-workflows - Best practices for sending documents, managing signing order, handling reminders

MCP Integration:

1. Connects to Signeasy MCP server (configurable via .mcp.json)
2. Uses ~~e-signature tool placeholder for provider-agnostic commands

Legal Plugin Updates

1. Added .mcp.json with e-signature MCP configuration
2. Updated CONNECTORS.md to reference e-signature integration
3. Enhanced /brief, /triage-nda, and /vendor-check commands with e-signature tool placeholders

Test plan

• Verify esignature plugin loads correctly with MCP server configured
• Test /signature-status returns pending document counts and account info
• Test /document-search finds documents by name
• Test /send-reminder sends reminder for a pending document
• Test /document-details shows signer breakdown for pending and signed documents
• Test /cancel-request confirmation flow
• Verify legal plugin commands reference e-signature tools appropriately