Add project scope documentation for AI playgroup registration system

Define complete non-technical scope for replacing Google Forms registration
with an AI-powered conversational agent. Includes:

- Registration data requirements (13 fields with validation rules)
- Knowledge base content (fees, regulations, schedule, FAQ from official PDFs)
- Conversation flow design with bilingual support (German/English)
- Agent personality guidelines (warm & friendly tone)
- Admin notification routing by playgroup type
- Email reminder system for incomplete registrations
- Data export formats (CSV/JSON)
- Channel configuration (email + chat)
- Release priorities (MVP scope defined)

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

openspec/changes/define-project-scope/specs/email-channel/spec.md

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+## ADDED Requirements
+
+### Requirement: System receives parent emails
+The system SHALL receive and process emails sent by parents to a designated registration email address.
+
+#### Scenario: Parent sends initial email
+- **WHEN** a parent sends an email to the registration address
+- **THEN** the system SHALL process the email and pass it to the AI agent
+
+#### Scenario: Parent replies to agent email
+- **WHEN** a parent replies to an email from the agent
+- **THEN** the system SHALL associate the reply with the existing conversation
+
+### Requirement: Agent responds via email
+The system SHALL send the AI agent's responses back to parents via email.
+
+#### Scenario: Agent sends response
+- **WHEN** the agent generates a response to a parent's message
+- **THEN** the system SHALL send an email to the parent with the response
+
+#### Scenario: Email formatting
+- **WHEN** an email is sent to a parent
+- **THEN** the email SHALL be properly formatted and readable in standard email clients
+
+### Requirement: Email conversations maintain state
+The system SHALL track email conversation threads and maintain registration state across multiple email exchanges.
+
+#### Scenario: Multi-email registration
+- **WHEN** a registration spans multiple email exchanges
+- **THEN** the system SHALL maintain context and collected data throughout the conversation
+
+#### Scenario: Conversation threading
+- **WHEN** a parent continues an existing registration conversation
+- **THEN** the system SHALL recognize the thread and resume from the previous state
+
+### Requirement: Email channel handles asynchronous communication
+The system SHALL handle the asynchronous nature of email without requiring immediate responses.
+
+#### Scenario: Delayed parent response
+- **WHEN** a parent takes hours or days to reply to an agent email
+- **THEN** the system SHALL still correctly process the reply and continue the conversation
+
+#### Scenario: Email delivery confirmation
+- **WHEN** an email is sent to a parent
+- **THEN** the system SHALL track delivery status for troubleshooting purposes