Story 18: Token-by-token streaming responses

- Backend: Added OllamaProvider::chat_stream() with newline-delimited JSON parsing
- Backend: Emit chat:token events for each token received from Ollama
- Backend: Added futures dependency and stream feature for reqwest
- Frontend: Added streamingContent state and chat:token event listener
- Frontend: Real-time token display with auto-scroll
- Frontend: Markdown and syntax highlighting support for streaming content
- Fixed all TypeScript errors (tsc --noEmit)
- Fixed all Biome warnings and errors
- Fixed all Clippy warnings
- Added comprehensive code quality documentation
- Added tsc --noEmit to verification checklist

Tested and verified:
- Tokens stream in real-time
- Auto-scroll works during streaming
- Tool calls interrupt streaming correctly
- Multi-turn conversations work
- Smooth performance with no lag

.living_spec/specs/tech/STACK.md

@@ -65,12 +65,24 @@ To support both Remote and Local models, the system implements a `ModelProvider`
 
 ### Rust
 *   **Style:** `rustfmt` standard.
+*   **Linter:** `clippy` - Must pass with 0 warnings before merging.
 *   **Error Handling:** Custom `AppError` type deriving `thiserror`. All Commands return `Result<T, AppError>`.
 *   **Concurrency:** Heavy tools (Search, Shell) must run on `tokio` threads to avoid blocking the UI.
+*   **Quality Gates:**
+    *   `cargo clippy --all-targets --all-features` must show 0 errors, 0 warnings
+    *   `cargo check` must succeed
+    *   `cargo test` must pass all tests
 
 ### TypeScript / React
-*   **Style:** Prettier / ESLint standard.
+*   **Style:** Biome formatter (replaces Prettier/ESLint).
+*   **Linter:** Biome - Must pass with 0 errors, 0 warnings before merging.
 *   **Types:** Shared types with Rust (via `tauri-specta` or manual interface matching) are preferred to ensure type safety across the bridge.
+*   **Quality Gates:**
+    *   `npx @biomejs/biome check src/` must show 0 errors, 0 warnings
+    *   `npm run build` must succeed
+    *   No `any` types allowed (use proper types or `unknown`)
+    *   React keys must use stable IDs, not array indices
+    *   All buttons must have explicit `type` attribute
 
 ## Libraries (Approved)
 *   **Rust:**