README: document the geo/cells_v1 manifest and what it does for warm reloads

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Richard Zink committed 2026-10-11 21:36:26 +02:00
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@@ -213,10 +213,15 @@ Everything is stored in IndexedDB, database `background-tiles`, store `tiles`:
| `geo/roadchains_v1` | merged road polylines (rebuilt only when a cell is re-fetched) | | `geo/roadchains_v1` | merged road polylines (rebuilt only when a cell is re-fetched) |
| `geo/placecache_v1` | decoded settlement list | | `geo/placecache_v1` | decoded settlement list |
| `geo/airports_v1` | airfield list used by the aviation layer | | `geo/airports_v1` | airfield list used by the aviation layer |
| `geo/cells_v1` | manifest: every cached Overpass cell with the time it was stored |
The star catalogue is not cached: `build.py` inlines `vendor/stars.json` into The star catalogue is not cached: `build.py` inlines `vendor/stars.json` into
`window.__starsData`. Weather is the only thing fetched live on every load. `window.__starsData`. Weather is the only thing fetched live on every load.
The manifest is what makes a warm reload fast: the road and settlement layers
compare `geo/cells_v1` against their build records and replay the finished
geometry without reading a single raw Overpass cell.
Cached data is never re-fetched unless `CONFIG.tiles.expireDays` is set. To Cached data is never re-fetched unless `CONFIG.tiles.expireDays` is set. To
start clean, delete the `background-tiles` database in the browser. start clean, delete the `background-tiles` database in the browser.