refactor(RPC): streamline handler delegation and improve FS compatibility

- Centralized fallback handling for RPC methods that should be Track effects using `rpc_method_should_be_effect` helper, reducing code duplication and improving error consistency.
- Added "fsPath" field to URI component responses in `path_to_uri_components_value` to align with VS Code extension expectations.
- Removed individual language feature registration stubs in favor of a consolidated `CatchAllRegisterProvider` method, reflecting Track's effect-based routing.
- Implemented proper TerminalService handlers leveraging `handlers::terminal` functions instead of placeholder implementations.
- Standardized FS API parameter handling with explicit VS Code default behaviors for create/overwrite options.
- Improved error logging in filesystem operations and URI conversion failures.
- Hardcoded "cocoon-main" sidecar ID in command handlers to simplify MVP implementation.

Author: NikolaRHristov