refactor(ollama)!: remove Ollama provider crate and implementation

Deletes the `owlen-ollama` Cargo.toml and source files, fully removing the Ollama provider from the workspace. This aligns the project with the MCP‑only architecture and eliminates direct provider dependencies.

crates/owlen-cli/Cargo.toml

@@ -26,7 +26,6 @@ required-features = ["chat-client"]
 owlen-core = { path = "../owlen-core" }
 # Optional TUI dependency, enabled by the "chat-client" feature.
 owlen-tui = { path = "../owlen-tui", optional = true }
-owlen-ollama = { path = "../owlen-ollama" }
 log = { workspace = true }
 async-trait = { workspace = true }
 futures = { workspace = true }