chore: add .env.example with all supported env vars

Documents all environment variables used across the workflow engine:
- LLM config (base URL, API key, model)
- Cursor agent config (model, timeout, provider)
- Hermes agent config (model, timeout)
- Storage and display options

Fixes #205

.env.example

@@ -0,0 +1,50 @@
+# ──────────────────────────────────────────────
+# Workflow Engine — Environment Variables
+# ──────────────────────────────────────────────
+# Copy this file to .env and fill in the values.
+
+# ── LLM (used by workflow-template-develop for AI-assisted coding) ──
+
+# OpenAI-compatible base URL for LLM calls
+# Default: https://dashscope.aliyuncs.com/compatible-mode/v1
+WORKFLOW_LLM_BASE_URL=
+
+# API key for LLM calls (required when using LLM features)
+WORKFLOW_LLM_API_KEY=
+
+# Model name for LLM calls
+# Default: qwen-plus
+WORKFLOW_LLM_MODEL=
+
+# ── Cursor Agent ──
+
+# Model override for Cursor agent
+WORKFLOW_CURSOR_MODEL=
+
+# Timeout in milliseconds for Cursor agent operations
+WORKFLOW_CURSOR_TIMEOUT=
+
+# LLM provider for Cursor agent (e.g. anthropic, openai)
+WORKFLOW_CURSOR_LLM_PROVIDER=
+
+# ── Hermes Agent (used by workflow-template-solve-issue) ──
+
+# Model override for Hermes agent
+WORKFLOW_HERMES_MODEL=
+
+# Timeout in milliseconds for Hermes agent operations
+WORKFLOW_HERMES_TIMEOUT=
+
+# ── Storage ──
+
+# Override the workflow storage root directory
+# Default: ~/.uncaged/workflow
+WORKFLOW_STORAGE_ROOT=
+
+# Gateway secret for the serve command
+WORKFLOW_GATEWAY_SECRET=
+
+# ── Display ──
+
+# Set to any value to disable colored output
+# NO_COLOR=1