feat(kernel-store): support absolute database paths

Modify `getDBFilename` to detect and pass through absolute paths
unchanged, instead of always joining them with the base directory. This
enables the daemon to store its database at a fixed location outside the
default relative path (e.g. `~/.ocap/kernel.db`).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: grypez

packages/kernel-store/src/sqlite/nodejs.test.ts

@@ -200,6 +200,14 @@ describe('makeSQLKernelDatabase', () => {
         recursive: true,
       });
     });
+
+    it('returns absolute path as-is and ensures parent directory exists', async () => {
+      const result = await getDBFilename('/home/user/.ocap/store.db');
+      expect(result).toBe('/home/user/.ocap/store.db');
+      expect(mockMkdir).toHaveBeenCalledWith('/home/user/.ocap', {
+        recursive: true,
+      });
+    });
   });
 
   describe('savepoint functionality', () => {

packages/kernel-store/src/sqlite/nodejs.ts

@@ -3,7 +3,7 @@ import type { Database as SqliteDatabase } from 'better-sqlite3';
 import Sqlite from 'better-sqlite3';
 import { mkdir } from 'node:fs/promises';
 import { tmpdir } from 'node:os';
-import { join } from 'node:path';
+import { dirname, isAbsolute, join } from 'node:path';
 
 import {
   SQL_QUERIES,
@@ -334,6 +334,10 @@ export async function getDBFilename(label: string): Promise<string> {
   if (label.startsWith(':')) {
     return label;
   }
+  if (isAbsolute(label)) {
+    await mkdir(dirname(label), { recursive: true });
+    return label;
+  }
   const dbRoot = join(tmpdir(), './ocap-sqlite', getDBFolder());
   await mkdir(dbRoot, { recursive: true });
   return join(dbRoot, label);