fix(logging): route diagnostic logs to stderr to prevent stdio transport corruption (#15)

[Lesnak1]

Summary

Fixes #15.

In the Model Context Protocol (MCP) stdio transport specification, stdout is strictly reserved for JSON-RPC protocol message frames ({"jsonrpc":"2.0",...}).

Previously, sidebar.ts and tools.ts logged diagnostic messages using console.log() to stdout (including dumping raw fetched markdown sidebar content). When MCP clients (Claude Desktop, Cursor, Zed, Goose, Antigravity) parse stdout, non-JSON text intermingled with JSON-RPC payloads corrupts the message stream and causes JSON parsing crashes.

Changes

• sidebar.ts: Replaced console.log() with console.error() for diagnostic logs and removed the raw markdown dump (console.log(sidebarContent)) to keep stdout completely clean.
• tools.ts: Replaced all console.log() calls with console.error() across the getGuide workflow.

Verification

• Verified that all diagnostic output routes to stderr, preserving valid JSON-RPC framing on stdout.
• Tested tool execution with MCP clients without protocol parse errors.