fix: resolve MCP -32601 error with Continue extension & fix CLI compilation

[AmineC95]

Description

This PR fixes an initialization error when using ruvector-mcp with the Continue VS Code extension, and resolves a missing feature compilation issue for the CLI.

Changes Made

1. Added resources/templates/list handler: The Continue extension calls this MCP method on startup. Since it was missing, it threw a -32601 Method not found error in the editor. I added a handler in handlers.rs that returns an empty resourceTemplates array to satisfy the client and prevent the error popup.
2. Fixed tokio dependency in CLI: Added the io-std feature to tokio in crates/ruvector-cli/Cargo.toml to resolve a cannot find function stdin in module tokio::io error when building the MCP server standalone.

Testing

• Compiled successfully on Windows using cargo build --release -p ruvector-cli --bin ruvector-mcp.
• Tested locally with the Continue VS Code extension: the MCP server now initializes cleanly without any error prompts and connects successfully.

[ruvnet]

Thanks @AmineC95! Clean fix for the MCP -32601 error.

• Adding the resources/templates/list handler with an empty response is the correct approach per the MCP spec
• The tokio io-std feature addition is needed for stdin transport

Looks good, no concerns.