fix(handbook): replace hardcoded version strings with dynamic components

[nerdalytics]

Summary

• Add resolveVersionLabel() to derive actual version label from URL prefix
• Add Version.svelte and VersionLink.svelte components that read version from Svelte context
• Set version context in DocLayout.svelte so all mdsvex pages can access it
• Replace hardcoded version strings across architecture (13), introduction (13), select (12), and llms (14) pages
• Historical references to prior versions stay hardcoded

Closes #93

Test plan

• npm run check passes (0 errors)
• Handbook builds successfully (cd handbook && npm run build)
• Spot-check /latest, /v1000.3.2, and /v1000.1.0 pages render correct version