fix(docs): restore version and discovery correctness

[mattsse]

Summary

• centralize the documented Alloy and Alloy Core versions and verify generated dependency snippets in CI
• configure the canonical site URL, sitemap, robots policy, page metadata, and working Open Graph image
• remove retired community references and replace shared RPC defaults with caller-supplied environment variables
• move example templates outside the routed pages tree
• replace the stale monolithic prompting page with a concise retrieval and verification guide for coding agents
• make the examples generator safer and keep it aligned with the new template location

Why

The live site mixed Alloy 0.x, 1.x, 2.0, and 2.1 guidance, lacked a sitemap and canonical page URLs, exposed internal templates through public routes, and embedded shared infrastructure endpoints in runnable snippets. The prompting page duplicated most of the manual and recommended obsolete dependencies and feature names, which made the machine-readable corpus actively misleading.

Impact

Installation and individual-crate declarations now target the versions shown by the site, dependency snippets cannot drift unnoticed, public pages have canonical metadata, sitemap and robots files are generated, and 15 internal templates disappear from public routing. Networked snippets require explicit RPC_URL or WS_URL configuration, avoiding brittle shared endpoints and accidental credential patterns. Coding agents receive a short workflow that prioritizes canonical pages, runnable examples, exact docs.rs symbols, and compiler verification.