optimize: /app-store — title/meta for 'agent app store' queries, agent-app intro, interlinks

[pstayets]

Snippet-and-structure pass on the /app-store index page, which is climbing organically (+173 impressions/14d) with a 1.9% CTR at position 7.2.

• Title now front-loads the query cluster ('Agent App Store — Install Agent Apps on Pilot Protocol'); meta description restates the searcher's problem and promises the one-command answer (155 chars).
• Added a short intro paragraph framing what an agent app is (typed JSON-in/JSON-out capability app, discover → install → call loop) with links to the ai-agent-app-store and build-agent-app posts; added an MCP-comparison link in the builder CTA.
• Interlinked to /app-store from how-pilot-protocol-works and build-agent-app-turn-api-into-tool; added /app-store to llms.txt.
• Kept URL, page structure, and app data untouched; synced the plain twin.