PDD-CLI Bug: Generates Feature Code Without Required Environment Configuration

## PDD-CLI Bug: Generates Feature Code Without Required Environment Configuration

PDD-CLI implements features that require environment variables or configuration settings, but doesn't generate the required `.env` entries or configuration files. Features fail at runtime due to missing configuration.

**Why this matters:** Generated features crash immediately with "missing environment variable" errors.

## Concrete Example

For an email sending feature:

```python
# PDD generated feature (INCOMPLETE):
# email_service.py
import brevo

def send_email(to: str, subject: str, body: str):
    client = brevo.Client(api_key=os.getenv('BREVO_API_KEY'))
    client.send(
        to=to,
        from_email=os.getenv('BREVO_SENDER_EMAIL'),  # ← Not in .env!
        from_name=os.getenv('BREVO_SENDER_NAME'),    # ← Not in .env!
        subject=subject,
        html=body
    )
```

But `.env` file has no configuration:

```bash
# .env (MISSING REQUIRED VARS)
BREVO_API_KEY=xxx
# Missing: BREVO_SENDER_EMAIL
# Missing: BREVO_SENDER_NAME
```

**What went wrong:** PDD implemented email sending but didn't add the required sender configuration to `.env.example` or document what values are needed.

**Impact:** Runtime error: `KeyError: 'BREVO_SENDER_EMAIL'` or emails fail silently with missing sender info.

## Why PDD Makes This Mistake

PDD-CLI currently:
- Generates feature code in isolation
- Doesn't track environment dependencies
- Doesn't update configuration files

But it should:
1. Identify required environment variables in generated code
2. Update `.env.example` with new variables and documentation
3. Add to README/docs what configuration is needed

## How to Prevent This in PDD-CLI

**What PDD should do differently:**

1. **Generate complete configuration:**
   ```python
   # When generating email_service.py, also update:
   
   # .env.example
   BREVO_API_KEY=your_api_key_here
   BREVO_SENDER_EMAIL=noreply@example.com
   BREVO_SENDER_NAME=Your App Name
   ```

2. **Document configuration requirements:**
   ```markdown
   # README.md
   ## Email Configuration
   Set the following environment variables:
   - `BREVO_API_KEY`: API key from Brevo dashboard
   - `BREVO_SENDER_EMAIL`: Verified sender email address
   - `BREVO_SENDER_NAME`: Display name for sender
   ```

3. **Validate configuration at startup:** Generate validation code that checks required vars exist.

**Example improvement:**
```
Current: "Add email feature"
       → Generate email_service.py
       → Missing .env configuration
       → Runtime failures

Improved: "Add email feature"
        → Generate email_service.py
        → Update .env.example with BREVO_* vars
        → Add config validation in startup
        → Document in README
        → Complete, working feature
```

## Severity

**P1 - High Priority**

- **Frequency:** Medium - affects features needing external services
- **Impact:** High - features completely broken until manually configured
- **Detectability:** High - immediate runtime errors
- **Prevention cost:** Low - track env vars during generation

## Category

`incomplete-implementation`

## Related Issues

- #433 - Handlers not wired up to runtime (similar "forgot to connect" issue)
- #432 - Data models without extraction logic (incomplete implementation)

---

**For Contributors:** Discovered when email sending feature crashed with missing `BREVO_SENDER_EMAIL` and `BREVO_SENDER_NAME` configuration, fixed in commit `34a651d5`.


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PDD-CLI Bug: Generates Feature Code Without Required Environment Configuration #583