refactor(core): remove provider module, migrate to LLMProvider, add client mode handling, improve serialization error handling, update workspace edition, and clean up conditionals and imports

docs/architecture.md

@@ -31,7 +31,7 @@ A simplified diagram of how components interact:
 
 ## Crate Breakdown
 
--   `owlen-core`: Defines the `LLMProvider` abstraction, routing, configuration, session state, encryption, and the MCP client layer. This crate is UI-agnostic and must not depend on concrete providers, terminals, or blocking I/O.
+-   `owlen-core`: Defines the `LlmProvider` abstraction, routing, configuration, session state, encryption, and the MCP client layer. This crate is UI-agnostic and must not depend on concrete providers, terminals, or blocking I/O.
 -   `owlen-tui`: Hosts all terminal UI behaviour (event loop, rendering, input modes) while delegating business logic and provider access back to `owlen-core`.
 -   `owlen-cli`: Small entry point that parses command-line options, resolves configuration, selects providers, and launches either the TUI or headless agent flows by calling into `owlen-core`.
 -   `owlen-mcp-llm-server`: Runs concrete providers (e.g., Ollama) behind an MCP boundary, exposing them as `generate_text` tools. This crate owns provider-specific wiring and process sandboxing.
@@ -131,3 +131,5 @@ The TUI is rendered on each iteration of the main application loop in `owlen-tui
 3.  **UI Composition**: Inside the closure, the UI is built by composing `ratatui` widgets. The root UI is defined in `owlen_tui::ui::render`, which builds the main layout and calls other functions to render specific components (like the chat panel, input box, etc.).
 4.  **State-Driven Rendering**: Each rendering function takes the current application state as an argument. It uses this state to decide what and how to render. For example, the border color of a panel might change if it is focused.
 5.  **Buffer and Diff**: `ratatui` does not draw directly to the terminal. Instead, it renders the widgets to an in-memory buffer. It then compares this buffer to the previous buffer and only sends the necessary changes to the terminal. This is highly efficient and prevents flickering.
+
+The command palette and other modal helpers expose lightweight state structs in `owlen_tui::state`. These components keep business logic (suggestion filtering, selection state, etc.) independent from rendering, which in turn makes them straightforward to unit test.

docs/provider-implementation.md

@@ -36,7 +36,7 @@ In your new crate's `lib.rs`, you will define a struct for your provider and imp
 ```rust
 use async_trait::async_trait;
 use owlen_core::model::Model;
-use owlen_core::provider::Provider;
+use owlen_core::Provider;
 use owlen_core::session::Session;
 
 pub struct MyProvider;