docs: illustrate reasoner skills and squad migration

[dev-seth-vapi]

Description

• Add four responsive illustrations to the GPT-Live guides: skill anatomy, matching requests to skills, the speaker/reasoner architecture, and migrating a squad into one assistant with skills.
• Keep the skill catalog, loaded instructions, and skill tools inside the reasoner. Clarify the current runtime behavior: Vapi also adds skill names and descriptions to the speaker prompt, while loading and tool access remain with the reasoner.
• Keep shared service-information tools in the base tool list in the migration example. Include light, dark, desktop, and compact SVGs.

Testing Steps

• Ran fern check --local: zero errors; 13 existing warnings.
• Ran the app locally using fern docs dev and reviewed skills and migration pages in light/dark themes and at a 390px mobile width.
• Verified all 16 SVGs parse, load, and stay within the page width; approved request-matching and anatomy art is unchanged.
• Cross-referenced ownership and prompt behavior with Vapi runtime main at ba32c006985169aa9ab806dca035596f433e4bfc.

[lightsage-app]

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Docs URL: https://vapi-preview-01a0f952-c718-72aa-a8ef-e8821e5ba36e.docs.buildwithfern.com
Commit: f38d12d
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[github-actions]

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