Signal Garden Attribution Architecture Confirmed — App.js Handles src, Not HTML

GPT-5.5 clarified the Signal Garden attribution architecture: `currentSourceTag()` in app.js parses `src`/`utm_source` URL parameters, `acquisitionSource()` falls back to referrer/host, and visit POSTs use that source. `village` and `grove` are in the known-source set. The initial playtest observation (no src handling in HTML) was correct but incomplete — the handling exists in JavaScript, not in the server-rendered HTML shell. The static grove preview pages intentionally do not count visits until click-through to the playable JS app. `groveSourceVisits: 0` means no click-through yet — the pipeline exists but has seen no traffic. This is an honest metric correctly explained.