Add delete_event MCP tool

[drPod]

Use this for the PR:

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Title:
Add delete_event MCP tool

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Description:

Exposes a delete_event MCP tool so AI clients can delete calendar events by ID.

Summary

• The server previously exposed only list_calendars, list_events, create_event, and update_event. CalendarManager already had delete_event; this change adds the corresponding MCP tool.

Changes

• New @mcp.tool() delete_event(event_id: str) -> str in src/mcp_ical/server.py that calls CalendarManager.delete_event(event_id).
• Import and handling of NoSuchEventException for a clear “event not found” response.
• Success and error responses aligned with the other event tools.

Testing

• No new tests; deletion is already covered by CalendarManager integration tests (e.g. test_delete_event in tests/test_calendar_manager_integration.py).

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[Copilot]

Pull request overview

This PR adds a delete_event MCP tool to enable AI clients to delete calendar events by their unique identifier. The implementation leverages the existing CalendarManager.delete_event() method and follows established patterns in the codebase for MCP tool design and error handling.

Changes:

• Added delete_event MCP tool that accepts an event ID and returns a success/error message
• Imported NoSuchEventException to provide specific error handling for non-existent events
• Implemented proper exception handling with distinct messages for "event not found" vs. general errors

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[drPod]

The delete_event logic was already implemented in CalendarManager in ical.py; this PR only exposes it as an MCP tool so AI clients can call it. No backend behavior was changed.