feat: Connection store with validation

[ggfevans]

Parent Epic

Part of #362 (Connection Graph Model - Port-Based Architecture)

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Summary

Implement a connection store with CRUD operations and validation logic for port-based connections.

Acceptance Criteria

• Create src/lib/stores/connection.svelte.ts
• addConnection(a_port_id, b_port_id, props) method
• updateConnection(id, updates) method
• removeConnection(id) method
• getConnection(id) method
• getConnectionsForPort(port_id) method
• getConnectionsForDevice(device_id) method
• Validation: port can only have one connection (error)
• Validation: incompatible port types (warning)
• Validation: same connection class required
• Undo/redo support via raw operations
• Dirty state tracking

Validation Rules

1. Single connection per port: Most ports allow only one connection. Error if already connected.
2. Type compatibility: Warning if connecting mismatched types (e.g., RJ45 to SFP).
3. Class match: Network ports only connect to network ports, power to power.
4. Self-connection: Cannot connect a port to itself.
5. Duplicate: Cannot create duplicate connection between same ports.

API

interface ConnectionStore {
  // Getters
  connections: Connection[];
  getConnection(id: string): Connection | undefined;
  getConnectionsForPort(portId: string): Connection[];
  getConnectionsForDevice(deviceId: string): Connection[];
  
  // CRUD
  addConnection(input: CreateConnectionInput): { connection: Connection } | { errors: string[] };
  updateConnection(id: string, updates: Partial<Connection>): { success: true } | { errors: string[] };
  removeConnection(id: string): Connection | undefined;
  removeConnectionsForDevice(deviceId: string): number;
  
  // Raw operations (for undo/redo)
  addConnectionRaw(connection: Connection): void;
  updateConnectionRaw(id: string, updates: Partial<Connection>): void;
  removeConnectionRaw(id: string): void;
  
  // Validation
  validateConnection(input: CreateConnectionInput): ValidationResult;
}

Test Requirements

• addConnection creates valid connection
• Double-connecting a port raises error
• Type mismatch raises warning
• Self-connection raises error
• Duplicate connection raises error
• removeConnectionsForDevice removes all connections for device
• Undo/redo works for connection operations
• Dirty state updates on changes

Related

• Parent Epic: feat: Connection Graph Model - Phase 1: Port-Based Architecture #362
• Depends on: feat: PlacedPort schema and port instantiation #363 (PlacedPort), feat: Connection model refactor (port-ID based) #365 (Connection)
• Similar to: Cable store from PR feat: cable data model and schema (#261) #355 (refactored)