CLI Extensions — Stage 8: app-demo integration polish + docs audit #267

Part of the EdgeZero CLI Extensions effort — stage 8 of 8.

Scope: make app-demo the full-capability showcase across all four adapters — app-demo-cli with all five built-ins plus Auth / Provision / Config (Validate | Push); handlers exercising multi-store KV (named()), async config, the nested config section, env-var override, and both secret forms; manual Spin secret-variable declarations in spin.toml. Add the missing CI wiring so the app-demo end-to-end loop actually runs (with explicit server-readiness, port selection, and teardown). Write docs/guide/cli-walkthrough.md. Run the §6.12 documentation audit — grep docs/ for stale references (old [stores.*] keys, the dev subcommand, the old singular store API) and fix every hit; confirm the docs/.vitepress/config.mts sidebar is complete.

Ship gate: CI runs the full loop on axum end-to-end; the documentation audit passes with zero stale references; all gates green.

Design spec: §15, §6.12 — Implementation plan: Stage 8.