docs: scaffold agent instruction tree

Add AGENTS.md, CLAUDE.md, and the agents-docs/ tree (workflow, lessons,
engineering standards, context map, ADR seed, feature template) plus a
domain-bearing CONTEXT.md for each of the six subdomains: toju-app,
electron, server, e2e, website, docs-site.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

agents-docs/features/feature-template.md

@@ -0,0 +1,183 @@
+# [Feature Name]
+
+> **Area:** [area-name]
+> **Status:** Active | In Progress | Deprecated
+> **Last updated:** YYYY-MM-DD
+
+## Overview
+
+One paragraph describing what this feature does and why it exists.
+
+## Responsibilities
+
+- What this feature is responsible for
+- Its boundaries — what it does NOT own
+
+## Key concepts
+
+- **ConceptA**: short definition
+- **ConceptB**: short definition
+
+---
+
+## API Endpoint
+
+### Endpoint Details
+- **Method**: [GET | POST | PUT | PATCH | DELETE]
+- **Path**: `/api/v1/[feature-path]`
+- **Authentication**: [Required | Optional | None]
+- **Rate Limiting**: [Yes — describe | No]
+
+### Request Schema
+
+```json
+{
+  "field": "type — description"
+}
+```
+
+**Required fields:**
+- `field` (type, constraints): description
+
+**Optional fields:**
+- `field` (type): description. Defaults to "X" if not provided.
+
+### Response Schema
+
+```json
+{
+  "field": "type — description"
+}
+```
+
+### Error Responses
+
+- **400 Bad Request**: [specific causes]
+- **401 Unauthorized**: missing or invalid authentication
+- **404 Not Found**: [when this applies]
+- **500 Internal Server Error**: [specific causes]
+
+---
+
+## Business Logic
+
+### Core Functionality
+
+1. **Step 1**: description
+2. **Step 2**: description
+3. **Step 3**: description
+
+### Business Rules
+
+- Rule 1
+- Rule 2
+
+### Data Flow
+
+```
+Input → Validation → [Processing Steps] → Response
+```
+
+### Dependencies
+
+- **Service/Library**: what it's used for
+- **External API**: what it's used for
+- **Database**: what tables/collections are involved
+
+---
+
+## Technical Implementation
+
+### Service Layer
+
+- **Location**: `path/to/service`
+- **Key methods**: `methodName()` — description
+
+### Controller / Handler
+
+- **Location**: `path/to/handler`
+- **Responsibilities**: request validation, service invocation, response formatting
+
+### Repository / Data Access
+
+- **Location**: `path/to/repository`
+- **Tables/Collections**: list the relevant database objects
+- **Migrations**: reference the migration that created/modified the schema
+
+### Key Types
+
+- `TypeName`: description of what it represents
+
+---
+
+## Configuration
+
+### Environment Variables
+
+- `VAR_NAME`: description (required | optional, default: X)
+
+### Feature Flags
+
+- [List any feature flags, or "None"]
+
+---
+
+## Testing
+
+### Unit Tests
+
+- **Location**: `path/to/tests`
+- **Key scenarios**: list the most important test cases
+
+### Integration Tests
+
+- **Location**: `path/to/integration/tests`
+- **Setup**: describe any required infrastructure (database, external services, etc.)
+- **Mocking**: what external services are mocked and how
+
+---
+
+## Error Handling & Edge Cases
+
+### Common Errors
+
+- **Error scenario**: how it's handled
+
+### Edge Cases
+
+- **Edge case**: expected behavior
+
+---
+
+## Security Considerations
+
+- Authentication requirements
+- Authorization / access control
+- Input validation and sanitization
+- Data privacy considerations
+
+---
+
+## Performance Considerations
+
+- Expected response times
+- Known bottlenecks
+- Caching strategy (if any)
+
+---
+
+## Known Issues and Limitations
+
+1. **Limitation**: description
+
+---
+
+## Related Features
+
+- **[Related Feature]**: brief description of relationship
+
+## Changelog
+
+| Date | Change |
+|------|--------|
+| YYYY-MM-DD | Initial documentation |