test: add unit tests for WelcomeComponent

[corvid-agent]

Summary

WelcomeComponent has a spec.md (added in #68) but no unit test file. The component has two async methods (onCreateSpec, onImport) with meaningful branching logic that should be tested.

Recommended test cases

Scenario	Description
Create spec → navigates	onCreateSpec() calls store.createSpec() and navigates to /edit/:id
Create spec → no id	If createSpec() returns without id, no navigation
Import single file	File picker → read → importMarkdownFiles() → navigate to last spec
Import multiple files	Multiple files imported, navigates to the last one
Import cancelled	No files selected → no action
Import returns 0	importMarkdownFiles() returns 0 → no navigation

Files

• Source: src/app/components/welcome/welcome.ts
• Spec: specs/components/welcome.spec.md
• Test (to create): src/app/components/welcome/welcome.spec.ts