[CG-16] Publish Code Cities online (static, on-demand loading)

[jgrodziski]

Priority: P1
Owner: David ("I can do it as-is on the snapshot, so we have something to show")

Description

Keep the site static. Host the JSONL on object storage (Cloudflare), load on demand so the docs site isn't slowed down (remote JSONL loading already works). Embed the city with a city selector. Define the update procedure. Long term: same code ships as a Tauri desktop app and as the online version.

Open: on the docs site, or a dedicated site?

Acceptance criteria

• At least one city reachable online
• Documented update procedure

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Source: CodeGraph backlog extracted from the 2026-09-21 weekly (David / Jérémie).