Enhance countdown-py README with comprehensive documentation

Added comprehensive documentation for the Python countdown example:

**Content Added:**
- Problem statement (resource waste, crash recovery)
- Solution explanation (durable sleep benefits)
- Real-world use cases (reminders, SLA monitors, rate limiting)
- Step-by-step code walkthrough
- Crash recovery explanation
- Running instructions with example commands
- Configuration options (ntfy.sh, Slack, Discord)
- Failure scenario testing procedures
- Key concepts (durable sleep, idempotency, resource efficiency)
- Production considerations
- Related examples

**Structure:**
- Clear sections with progressive detail
- Code examples with explanations
- Testing procedures for crash recovery
- Multiple notification backend examples

Updated repo description and topics: resonate, python, durable-execution,
countdown, notifications

Note: Removed serverless/cloud function sections as Python SDK does not
yet have shims for those platforms.

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: flossypurse

README.md

@@ -1 +1,211 @@
-# example-countdown-py
+# Example: Countdown with Durable Sleep (Python)
+
+A countdown timer that demonstrates **durable sleep** - long pauses without consuming resources, surviving crashes and resuming exactly where it left off.
+
+## What This Demonstrates
+
+### Problem: Long-Running Timers
+Traditional countdown timers keep a process running continuously, wasting resources during sleep periods. If the process crashes, you lose the countdown state.
+
+### Solution: Durable Sleep
+Resonate's durable sleep allows workflows to:
+- Pause for extended periods (hours, days, weeks)
+- Consume zero resources while sleeping
+- Survive crashes and resume at the right time
+- Send periodic notifications reliably
+
+## Use Cases
+
+This pattern applies to:
+- **Scheduled reminders** - Meeting notifications, task deadlines
+- **SLA monitors** - Alert if response not received in time
+- **Rate limiting** - Enforce delays between operations
+- **Periodic reports** - Daily/weekly/monthly automation
+- **Countdown timers** - Track time until events
+
+## How It Works
+
+```python
+def countdown(ctx: Context, count: int, interval, url: str):
+    for i in range(count, 0, -1):
+        # Send notification (durable)
+        yield ctx.run(notify, message=f"Countdown: {i}", url=url)
+
+        # Sleep for interval (process can exit here)
+        yield ctx.sleep(interval)
+
+    # Final notification
+    yield ctx.run(notify, message="Countdown complete", url=url)
+```
+
+### What Happens on Each Iteration
+
+1. **Send notification** - `ctx.run()` executes and checkpoints the result
+2. **Sleep** - `ctx.sleep()` suspends the workflow, process can exit
+3. **Resume** - Resonate wakes the workflow after the interval
+4. **Repeat** - Continue from checkpoint without re-sending notifications
+
+### Crash Recovery
+
+If the process crashes during sleep:
+- Workflow state is preserved in Resonate
+- Resonate automatically resumes at the scheduled wake time
+- No notifications are duplicated
+- Countdown continues as if nothing happened
+
+## Running the Example
+
+### Prerequisites
+
+- Python 3.13+
+- uv (Python package manager)
+- ntfy.sh account or webhook URL
+
+### Installation
+
+```bash
+# Install dependencies
+uv sync
+```
+
+### Usage
+
+```bash
+# Start the countdown worker
+uv run python countdown.py
+```
+
+Then trigger a countdown via the Resonate API or another process:
+
+```bash
+# Start 10-minute countdown with 1-minute intervals
+curl -X POST http://localhost:8001/promises \
+  -H "Content-Type: application/json" \
+  -d '{
+    "id": "countdown/demo",
+    "timeout": 36000000,
+    "data": {
+      "func": "countdown",
+      "args": [10, 60000, "https://ntfy.sh/your-topic"]
+    }
+  }'
+```
+
+**Parameters:**
+- `count`: Number of countdown steps (10 = 10 notifications)
+- `interval`: Milliseconds between steps (60000 = 1 minute)
+- `url`: Webhook URL for notifications (ntfy.sh, Slack, etc.)
+
+### Notification Format
+
+Each notification sends JSON:
+```json
+{
+  "message": "Countdown: 7"
+}
+```
+
+## Configuration
+
+### Environment Variables
+
+Create a `.env` file:
+```bash
+RESONATE_URL=http://localhost:8001
+RESONATE_TOKEN=your-token-here
+NTFY_URL=https://ntfy.sh/your-topic
+```
+
+### Notification Backends
+
+The example uses ntfy.sh by default, but works with any webhook:
+
+**Slack:**
+```python
+url = "https://hooks.slack.com/services/YOUR/WEBHOOK/URL"
+```
+
+**Discord:**
+```python
+url = "https://discord.com/api/webhooks/YOUR/WEBHOOK"
+```
+
+**Custom API:**
+```python
+url = "https://api.example.com/notifications"
+```
+
+## Testing Failure Scenarios
+
+### Test 1: Crash During Sleep
+
+1. Start countdown with long interval:
+```bash
+# 5 steps, 30 seconds each
+resonate.run("test/crash", countdown, 5, 30000, url)
+```
+
+2. Wait for first notification
+
+3. Kill the process (Ctrl+C)
+
+4. Restart the process:
+```bash
+uv run python countdown.py
+```
+
+5. Observe: Countdown resumes at the correct step, no duplicates
+
+### Test 2: Long-Running Countdown
+
+```bash
+# 24-hour countdown with hourly notifications
+resonate.run("test/longrun", countdown, 24, 3600000, url)
+```
+
+Process can stop/start freely. Notifications arrive on schedule.
+
+## Code Structure
+
+```
+countdown.py    # Countdown workflow definition
+pyproject.toml  # Dependencies
+```
+
+## Key Concepts
+
+### Durable Sleep
+- `ctx.sleep(milliseconds)` suspends workflow
+- Process can exit, workflow state persists
+- Resonate resumes at the right time
+- No polling, no cron jobs needed
+
+### Idempotency
+- Each notification uses a deterministic ID
+- Replays don't duplicate notifications
+- `ctx.run()` checkpoints prevent re-execution
+
+### Resource Efficiency
+- Zero CPU/memory during sleep
+- Scale to zero between notifications
+- Pay only for active execution time
+
+## Production Considerations
+
+1. **Monitoring**: Track notification delivery success
+2. **Error handling**: Add retry logic for webhook failures
+3. **Timeouts**: Set workflow timeout longer than total countdown
+4. **Backpressure**: Limit concurrent countdown workflows
+5. **Observability**: Log each notification for audit trail
+
+## Learn More
+
+- [Python SDK Docs](https://docs.resonatehq.io/sdk/python)
+- [Durable Sleep Explained](https://docs.resonatehq.io/concepts/sleep)
+- [Serverless Patterns](https://docs.resonatehq.io/patterns/serverless)
+
+## Related Examples
+
+- [example-countdown-ts](../example-countdown-ts) - TypeScript version
+- [example-durable-sleep-py](../example-durable-sleep-py) - Basic sleep patterns
+- [example-durable-sleep-ts](../example-durable-sleep-ts) - Basic sleep patterns (TypeScript)