Align guide docs with the code on main #372

Description

The guide pages under docs/guide drifted from the code as the CLI extensions, store registries, State<T> / nested secrets, introspection routes, config gc, the deploy actions, and the Fastly custom entry-point exports (#351) landed. A page-by-page audit of every guide page against the current crates found three kinds of drift:

• Phantom names. dispatch_with_config / dispatch_with_config_handle (fastly, cloudflare, architecture), AxumProxyClient::default(), the EDGEZERO_SECRET_ prefix, wrangler secret put --binding, diff.rs::run_config_diff_typed, dispatch_with_*_handle, and crate-root imports for types that live in proxy::, context::, or dev_server::.
• Behaviour the code contradicts. Streaming claims (only Cloudflare preserves progressive delivery), route conflicts (panic at build, not first-registered-wins), Axum bind-address and logging sources, Axum KV file naming, healthcheck output and token behaviour, EDGEZERO_MANIFEST scope, Cloudflare local push selection, the deploy actions' Node 24 action list and cache-key components.
• Missing coverage. Fastly custom entry points (Docs: custom Fastly entry point section for runtime_env_config / dispatch_with_registries #361), the FastlyService / CloudflareService builders, store extractors, FnMiddleware, the app! argument list, adapter metadata and auth-* command overrides, EDGEZERO__LOGGING__* variables, config push --staging, Spin across the landing page / platform table / architecture / roadmap / adapter overview and its own page (Spin adapter documentation #77), Axum KV and secrets, Cloudflare secrets and the kv/config merged-id collision, and the KV page missing from the sidebar.

Done when

• Every page in docs/guide names only identifiers, flags, env vars, manifest keys, and subcommands that exist in the source tree.
• Behaviour descriptions on those pages match the code (streaming, routing conflicts, Axum runtime, healthcheck, manifest fallback, actions).
• docs/guide/kv.md is reachable from the sidebar.
• cd docs && npm run format && npm run lint && npm run build pass.

Affected area: Documentation