Remove dead code and unused files

- Remove unused unified_context.rs and unified_slash_command.rs
- Remove unused methods from knowledge_store.rs
- Clean up mod.rs imports
- No more compiler warnings

Author: kennvene-aws

crates/chat-cli/src/cli/chat/cli/mod.rs

@@ -12,7 +12,6 @@ pub mod prompts;
 pub mod resource;
 pub mod subscribe;
 pub mod tools;
-pub mod unified_context;
 pub mod usage;
 
 use clap::Parser;