fix: replace litellm with tiktoken for token counting

- litellm had dependency conflicts with pydantic-ai
- tiktoken is lighter and already required by pydantic-ai
- Updated documentation (README.md, architecture.md)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -4,8 +4,9 @@ A Claude Code-inspired development assistant powered by local LLMs via Ollama.
 
 ## Features
 
-- **Explore Agent** - Search, read, and understand codebases
-- **8 Tools** - File read/write, glob, grep, bash, web search
+- **3 Agents** - Explore (read-only), Plan (architecture), Task (orchestrator)
+- **8 Tools** - File read/write/edit, glob, grep, bash, web search
+- **Conversations** - Multi-turn memory with context summarization
 - **Streaming** - Real-time response display
 - **Self-hosted** - Runs on your own hardware with Ollama
 
@@ -74,11 +75,33 @@ webber-cli chat -d /path/to/project
 | `bash` | Full bash with safety controls |
 | `web_search` | Search web via SearXNG |
 
+## Agents
+
+| Agent | Purpose | Tools |
+|-------|---------|-------|
+| **Explore** | Fast codebase navigation, search | Read-only (glob, grep, read, bash_readonly) |
+| **Plan** | Design implementation strategies | Read-only (same as Explore) |
+| **Task** | Autonomous multi-step execution | All tools + spawn_agent |
+
+## API Endpoints
+
+```bash
+# Stateless agent execution
+POST /agents/run          # Execute agent, get response
+POST /agents/stream       # Execute with SSE streaming
+GET  /agents/             # List available agents
+
+# Stateful conversations (multi-turn memory)
+POST /conversations/              # Create conversation
+GET  /conversations/              # List conversations
+POST /conversations/{id}/messages # Add message, get agent response
+```
+
 ## Versioning
 
 This project uses prefixed tags for independent release cycles:
 
-- `api/v0.3.0` - Triggers API Docker build and deployment
+- `api/v0.4.0` - Triggers API Docker build and deployment
 - `cli/v0.1.0` - Triggers CLI installer build (future)
 
 ## Requirements