Improve Getting Started: show all config methods and Docker workflow

Show three ways to configure the CLI (env vars, config file, flags),
explain how to get the key from Docker Compose, and clarify that
TUI uses the same config. Make the Docker-to-CLI connection explicit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bricef

README.md

@@ -35,10 +35,28 @@ TASKFLOW_SEED_ADMIN_NAME=admin TASKFLOW_SEED_ADMIN_KEY=my-known-key ./taskflow-s
 
 ### 2. Configure the CLI
 
+Set the API key for the CLI (and TUI). All three methods work — use whichever fits your setup:
+
 ```bash
+# Option A: environment variables (good for quick use)
 export TASKFLOW_API_KEY=$(cat seed-admin-key.txt)
-# Or add to config file:
-# echo "api_key: $(cat seed-admin-key.txt)" >> ~/.config/taskflow/config.yaml
+export TASKFLOW_URL=http://localhost:8374    # default, only needed if server is elsewhere
+
+# Option B: config file (persistent)
+mkdir -p ~/.config/taskflow
+cat > ~/.config/taskflow/config.yaml <<EOF
+url: http://localhost:8374
+api_key: $(cat seed-admin-key.txt)
+EOF
+
+# Option C: flags (one-off commands)
+taskflow --url http://localhost:8374 --api-key <key> board list
+```
+
+For Docker Compose, the server is on `localhost:8374` by default. Get the key with:
+
+```bash
+export TASKFLOW_API_KEY=$(docker compose exec -T taskflow cat /data/seed-admin-key.txt)
 ```
 
 ### 3. Create a board and tasks
@@ -62,16 +80,19 @@ taskflow actor create --name alice --display_name "Alice Chen" --type human --ro
 taskflow actor create --name claude --display_name "Claude" --type ai_agent --role member
 ```
 
-The API key is returned in the response (shown once). Share it with the actor for CLI, TUI, or MCP configuration.
+The API key is returned in the response (shown once). Share it with the actor for their CLI, TUI, or MCP configuration.
 
 ### 5. Use other interfaces
 
 ```bash
-# TUI — interactive terminal UI
-TASKFLOW_API_KEY=<key> taskflow-tui
+# TUI — interactive terminal UI (uses same config as CLI)
+taskflow-tui
+
+# TUI — connect to a specific board directly
+taskflow-tui platform
 
-# MCP — AI agent integration (see docs/mcp.md)
-TASKFLOW_API_KEY=<agent-key> taskflow-mcp
+# MCP — AI agent integration (see docs/mcp.md for Claude Code setup)
+TASKFLOW_URL=http://localhost:8374 TASKFLOW_API_KEY=<agent-key> taskflow-mcp
 ```
 
 ## Documentation