Refactor IPC and DTO structures; remove unused code and streamline message handling

- Removed unused structs and methods from `response.rs`, `usage.rs`, and `client.rs`.
- Simplified `Connection` handling in `conn.rs` to only support Unix sockets.
- Updated `IpcServer` to exclusively use Unix sockets and removed TCP handling.
- Cleaned up `editlog.rs` by removing loading and recent entry methods.
- Refactored `memory.rs` to eliminate unused functions related to lesson promotion and retrospective creation.
- Enhanced `search.rs` to support multiple search providers and improved error handling.
- Updated chat view logic to simplify message display and improve user experience.
- Removed deprecated modules and constants from various files to streamline the codebase.

src/app/bgbash/control.rs

@@ -28,11 +28,3 @@ pub fn bash_kill(id: &str) -> anyhow::Result<()> {
         anyhow::bail!("bash job '{}' not found", id)
     }
 }
-
-pub fn register_bash_job(job: BashJob) -> String {
-    let id = job.id.clone();
-    if let Ok(mut map) = bash_jobs_map().lock() {
-        map.insert(id.clone(), job);
-    }
-    id
-}