Re-coarsen RU-ARK Arctic-coast band into RU-PEO + RU-YAM (#41)

#41: re-partition the RU-ARK mainland's 28-part lat>=68 Arctic-coast band
into two new regions via a new turf-free, idempotent pipeline stage
scripts/split-arkhangel-band.mjs (npm run split:regions:band), mirroring the
#31 split:

- RU-PEO (Pechora, 13 parts, ~37,678 km2) -> key pechora-qwhs
- RU-YAM (Yamal, 15 parts, ~51,722 km2) -> key yamal-gosw
- RU-ARK keeps its id/name/key arkhangel-sk-lhbk (ownership-safe); the 5-part
  lat<68 core (~305,229 km2) stays RU-ARK.

Pure re-partition: no geometry moved (byte-identical union). The two new
features are inserted immediately after RU-ARK-SZ. Manifests regenerated with
the real scripts (1,798 -> 1,800 keys + adjacency; adjacency pairs 4,471 ->
4,473). Fixed-point dataset unchanged except feature count (11,794 parts /
11,795 rings / 164,801 verts / 1 KZ-KZY hole). Four dataset/manifest tests
updated (RUS 82 -> 84 sub-regions). Version 0.25.0 -> 0.26.0.

Fixes #41

scripts/region-keys.test.ts

@@ -33,13 +33,13 @@ describe('region-keys.json', () => {
   const keys = Object.values(manifest);
   const featureIds = (geo.features ?? []).map((f) => String(f.id));
 
-  it('has exactly 1,798 entries (one per region)', () => {
-    expect(Object.keys(manifest)).toHaveLength(1798);
+  it('has exactly 1,800 entries (one per region)', () => {
+    expect(Object.keys(manifest)).toHaveLength(1800);
   });
 
-  it('has 1,798 unique keys (no collisions)', () => {
+  it('has 1,800 unique keys (no collisions)', () => {
     expect(new Set(keys).size).toBe(keys.length);
-    expect(new Set(keys).size).toBe(1798);
+    expect(new Set(keys).size).toBe(1800);
   });
 
   it('keys each end in -[a-z]{4} and contain at least one hyphen', () => {
@@ -50,21 +50,26 @@ describe('region-keys.json', () => {
     }
   });
 
-  it("keeps RU-ARK's key stable across the #31 split and mints the two island keys", () => {
-    // v0.25 (#31) split RU-ARK into main + RU-ARK-NE + RU-ARK-SZ. The MAIN
-    // feature keeps its id (and therefore its key — FNV-1a of the id), which
-    // is what keeps existing Nation.territory / SQLite ownership valid; the
-    // two new features get fresh keys derived the same way from their ids.
+  it("keeps RU-ARK's key stable across the #31 + #41 splits and mints the island and band keys", () => {
+    // v0.25 (#31) split RU-ARK into main + RU-ARK-NE + RU-ARK-SZ, and v0.26
+    // (#41) repartitioned the mainland into the core (RU-ARK) + RU-PEO +
+    // RU-YAM. The MAIN feature keeps its id (and therefore its key — FNV-1a
+    // of the id), which is what keeps existing Nation.territory / SQLite
+    // ownership valid; the new features get fresh keys derived the same way
+    // from their ids (no within-country name-collision salt needed — the
+    // slugs are unique).
     expect(manifest['RU-ARK']).toBe('arkhangel-sk-lhbk'); // unchanged since v0.19
     expect(manifest['RU-ARK-NE']).toBe('new-earth-eikt');
     expect(manifest['RU-ARK-SZ']).toBe('severnaya-zemlya-awqp');
+    expect(manifest['RU-PEO']).toBe('pechora-qwhs');
+    expect(manifest['RU-YAM']).toBe('yamal-gosw');
   });
 
   it('is a stable join: its keys are exactly the regions.geo.json feature ids', () => {
     // The manifest is looked up by feature id, so its key set must line up
     // 1:1 with the geo file (catches drift if the geo is regenerated without
     // rebuilding the keys).
-    expect(featureIds).toHaveLength(1798);
+    expect(featureIds).toHaveLength(1800);
     const manifestIds = Object.keys(manifest);
     expect(new Set(manifestIds)).toEqual(new Set(featureIds));
   });