Add Kiro IDE integration docs page

[marcel-rbro]

Problem

Kiro is listed under integrations as an IDE but has no dedicated docs page.

Context

Flagged by @LukasBekr in #product-ai: Slack message.

AWS is unlikely to open a PR for this themselves, so we should write the page on our side.

Scope (to confirm)

• Confirm scope with @LukasBekr (depth, where the page sits in the IA)
• Draft Kiro IDE integration page following existing IDE/integration page conventions
• Cross-link from the integrations index