5 — Add slug to Project interface, kill ternary chain

Problem: softwareNavItems in projects.ts has a hardcoded ternary chain:

p.name === 'concept-browser' ? 'concept-browser' : p.name === 'glossarist-desktop' ? 'desktop' : p.name

Adding a new project requires editing this chain. Violates Open/Closed.

Action:

• Add slug: string to Project interface
• Each project defines its own slug
• softwareNavItems uses p.slug

Files touched:

• .vitepress/data/projects.ts

Done when: softwareNavItems has no conditional logic.