docs: expand scope and add comprehensive documentation

Create README.md and enhance AGENTS.md to position this as an
extensible framework for any Opencode skills and agents, not just
PARA/task management. Includes installation, development workflow,
code style guidelines, and Nix flake integration patterns.

skill/communications/SKILL.md

@@ -0,0 +1,78 @@
+---
+name: communications
+description: "Email and communication management with Proton Mail integration. Use when: (1) drafting emails, (2) managing follow-ups, (3) communication tracking, (4) message templates, (5) inbox management. Triggers: email, draft, reply, follow up, message, inbox, communication, respond to."
+compatibility: opencode
+---
+
+# Communications
+
+Email and communication management for Proton Mail.
+
+## Status: Stub
+
+This skill is a placeholder for future development. Core functionality to be added:
+
+## Planned Features
+
+### Email Drafting
+- Context-aware draft generation
+- Tone matching (formal/casual)
+- Template-based responses
+
+### Follow-up Tracking
+- Waiting-for list management
+- Follow-up reminders
+- Response tracking
+
+### Inbox Management
+- Priority sorting
+- Quick triage assistance
+- Archive recommendations
+
+### Communication Templates
+- Common response patterns
+- Meeting request templates
+- Status update formats
+
+## Integration Points
+
+- **Proton Mail**: Primary email backend
+- **task-management**: Convert emails to tasks
+- **ntfy**: Important email alerts
+- **n8n**: Automation workflows
+
+## Quick Commands (Future)
+
+| Command | Description |
+|---------|-------------|
+| `draft reply to [context]` | Generate email draft |
+| `follow up on [topic]` | Check follow-up status |
+| `email template [type]` | Use saved template |
+| `inbox summary` | Overview of pending emails |
+
+## Proton Mail Integration
+
+API integration pending. Options:
+- Proton Bridge (local IMAP/SMTP)
+- n8n with email triggers
+- Manual copy/paste workflow initially
+
+## Communication Style Guide
+
+Based on Sascha's profile:
+- **Tone**: Professional but approachable
+- **Length**: Concise, get to the point
+- **Structure**: Clear ask/action at the top
+- **Follow-up**: Set clear expectations
+
+## Email Templates (Future)
+
+- Meeting request
+- Status update
+- Delegation request
+- Follow-up reminder
+- Thank you / acknowledgment
+
+## Notes
+
+Start with manual draft assistance. Proton Mail API integration can be added via n8n workflow when ready.