Dev: route the web's map through this stack's tile server; power grid offline

Two reasons an offline dev run's web client had no map:

1. Vite proxied every tile to the public tile host. web_command now sets
   ODIAN_TILE_SERVER_URL=http://127.0.0.1:18081 for the Vite it starts, and
   ODIAN_Engine's _WEB/vite.config.ts sends /basemap, /mvt and /netlayer there:
   the site while it answers, this PC's installed tiles when it does not - the
   same path the .exe already draws from.

2. The power-grid netlayer had no source offline. datasets.json named every
   PostGIS overlay but `powerv2_postgis`, so the tile server answered
   /netlayer/<ds>/powerv2/* with 404 "powerv2_render_sqlite not found" while
   postgis_power_entities / _links / _topology sat in the local snapshot. Added
   to POSTGIS_SOURCES; the tile server resolves it through the same
   ODIAN_TILE_POSTGIS_DSN as the others.

Spot-check: with the site unreachable, /netlayer/<ds>/powerv2/bbox/8/128/86/131/89.json
answers 200 (721064 B, the same body the site serves) and topology.bin 200.

src-tauri/src/stack.rs

@@ -627,6 +627,10 @@ fn web_command(dir: &Path) -> Command {
     .arg("--port")
     .arg(WEB_PORT.to_string())
     .arg("--strictPort")
+    // The map through THIS stack's tile server, as the .exe draws it: the site while it
+    // answers, this PC's installed tiles when it does not. Without it _WEB's proxy goes
+    // to the public tile host, and an offline run has no map at all.
+    .env("ODIAN_TILE_SERVER_URL", format!("http://127.0.0.1:{TILES_PORT}"))
     .current_dir(dir);
   web
 }
@@ -805,7 +809,9 @@ const TILES_POSTGIS_DSN_ENV: &str = "ODIAN_TILE_POSTGIS_DSN";
 /// launcher sets) leaves the layer with nowhere to read, and it draws nothing at all. That is
 /// what kept oil, gas, aeroways and military bases off an offline map while their tables sat
 /// in the database unused - only the four Theatre layers below were ever named here.
-const POSTGIS_SOURCES: [&str; 8] = [
+/// `powerv2_postgis` (the power grid netlayer) was the last one missing: its tables
+/// (`postgis_power_entities` / `_links` / `_topology`) are in the snapshot too.
+const POSTGIS_SOURCES: [&str; 9] = [
   "aeroway_postgis",
   "datacenter_postgis",
   "gas_postgis",
@@ -813,6 +819,7 @@ const POSTGIS_SOURCES: [&str; 8] = [
   "military_base_postgis",
   "oil_postgis",
   "place_of_worship_postgis",
+  "powerv2_postgis",
   "school_postgis",
 ];
 
@@ -1407,6 +1414,19 @@ mod tests {
     assert_eq!(cmd.get_current_dir(), Some(Path::new(r"E:\dev\ODIAN_Engine\_WEB")));
   }
 
+  #[test]
+  fn the_web_draws_its_map_from_this_stacks_tile_server() {
+    // Offline, the public tile host is unreachable; this stack's tile server still has
+    // the PC's installed tiles. _WEB's vite.config.ts reads this variable.
+    let cmd = web_command(Path::new(r"E:\dev\ODIAN_Engine\_WEB"));
+    let tiles = cmd
+      .get_envs()
+      .find(|(key, _)| *key == "ODIAN_TILE_SERVER_URL")
+      .and_then(|(_, value)| value)
+      .map(|value| value.to_string_lossy().into_owned());
+    assert_eq!(tiles.as_deref(), Some("http://127.0.0.1:18081"));
+  }
+
   #[test]
   fn a_query_value_cannot_end_its_own_parameter() {
     // The address is built here, but the operator name comes from a text field.
@@ -1547,7 +1567,8 @@ mod tests {
       }
       // The ones that were missing, named outright: they are why an offline map had
       // hospitals and schools but no oil, gas, aeroways or military bases.
-      for key in ["oil_postgis", "gas_postgis", "aeroway_postgis", "military_base_postgis"] {
+      // And the power grid, missing after that: offline, the web's power layer 404'd.
+      for key in ["oil_postgis", "gas_postgis", "aeroway_postgis", "military_base_postgis", "powerv2_postgis"] {
         assert_eq!(doc[dataset][key]["dsn_env"], TILES_POSTGIS_DSN_ENV, "{dataset} {key}");
       }
     }