Feature: Add ability to get loaded scripts

Summary

Add a new MCP tool called get_loaded_scripts that returns all scripts currently loaded in the active debug session.

Problem

When an AI agent wants to set a breakpoint, it currently has no way to know which files are actually loaded by the runtime. This forces the agent to guess file paths, which is a leading cause of breakpoints silently failing to bind (see #18). VS Code's Loaded Scripts explorer (visible in the Run & Debug sidebar) already shows this information — it just isn't surfaced through DebugMCP.

Proposed Solution

Add a get_loaded_scripts tool that uses the Debug Adapter Protocol loadedSources request via vscode.debug.activeDebugSession.customRequest('loadedSources', {}) to return the list of all sources loaded by the runtime.

Requirements:

• No parameters required
• Must work on a running debug session — does not require the session to be paused or stopped at a breakpoint
• Should return a clear error if no debug session is active
• Should return a graceful error if the debug adapter does not support loadedSources (it is an optional DAP capability — supported by Node.js, Electron, and Chrome-based adapters)

Start at the existing MCP tool entry point for adding get_loaded_scripts, then trace how it accesses vscode.debug.activeDebugSession. Use the loadedSources custom request while a debug session is running, and verify completion by checking the returned sources plus clear errors for no active session or unsupported adapters.