power user shortcut for MCP tool invocation

### Describe the feature or problem you'd like to solve

Add a syntax to invoke a specific mcp tool command

### Proposed solution

Fewer keystrokes
Unambiguous - no LLM interporetation lyaer
Tab-completable
Consistent with VSCode

### Example prompts or workflows

#mcp-server:tool arg1 arg2 style syntax

### Additional context

_No response_

The issue names no files, tests, or entry points. Start by locating the CLI parser, MCP tool invocation flow, and tab-completion implementation, then compare existing syntax with the referenced VSCode behavior. Done should include an unambiguous #mcp-server:tool arg1 arg2 form with completion and tests for invocation.

Written by the indexing model from the issue text.