fix(reference): verify station coverage and rollback inputs

tests/reference.test.ts

@@ -321,6 +321,25 @@ describe('fixture reference compiler', () => {
     } finally { await rm(root, { recursive: true, force: true }); }
   });
 
+  test('rejects incomplete PREVIOUS count metadata before rollback', async () => {
+    const { root, sources } = await fixtureDirectory();
+    const directory = join(root, 'reference');
+    try {
+      const first = await new ReferenceCompiler({ directory, profile: 'fixture', sources: fixtureSources(sources) }).compile();
+      expect(first.status).toBe('success');
+      if (first.status !== 'success') throw new Error('initial fixture build did not publish');
+      await writeFile(join(sources, 'reference-data.json'), `${await readFile(join(sources, 'reference-data.json'), 'utf8')}\n`);
+      const second = await new ReferenceCompiler({ directory, profile: 'fixture', sources: fixtureSources(sources) }).compile();
+      expect(second.status).toBe('success');
+      const manifest = await readReferenceManifest(directory);
+      if (!manifest.previous) throw new Error('fixture build did not retain PREVIOUS');
+      const malformed = { ...manifest, previous: { ...manifest.previous, counts: Object.fromEntries(Object.entries(manifest.previous.counts).filter(([key]) => key !== 'stations')) } };
+      await writeFile(join(directory, 'manifest.json'), `${JSON.stringify(malformed)}\n`);
+      await expect(new ReferenceCompiler({ directory, profile: 'fixture', sources: fixtureSources(sources) }).rollback()).rejects.toThrow(/missing count metadata/);
+      expect((await readReferenceManifest(directory)).active?.version).toBe(manifest.active?.version);
+    } finally { await rm(root, { recursive: true, force: true }); }
+  });
+
   test('recovers a validated orphan database after manifest publication crash', async () => {
     const { root, sources } = await fixtureDirectory();
     const directory = join(root, 'reference');