feat(memory): add explicit paths config for memory search

Add a `paths` option to `memorySearch` config, allowing users to
explicitly specify additional directories or files to include in
memory search.

Follow-up to #2961 as suggested by @gumadeiras — instead of auto-following
symlinks (which has security implications), users can now explicitly
declare additional search paths.

- Add `memorySearch.paths` config option (array of strings)
- Paths can be absolute or relative (resolved from workspace)
- Directories are recursively scanned for `.md` files
- Single `.md` files can also be specified
- Paths from defaults and agent overrides are merged
- Added 4 test cases for listMemoryFiles

src/memory/sync-memory-files.ts

@@ -14,6 +14,7 @@ type ProgressState = {
 
 export async function syncMemoryFiles(params: {
   workspaceDir: string;
+  additionalPaths?: string[];
   db: DatabaseSync;
   needsFullReindex: boolean;
   progress?: ProgressState;
@@ -27,7 +28,7 @@ export async function syncMemoryFiles(params: {
   ftsAvailable: boolean;
   model: string;
 }) {
-  const files = await listMemoryFiles(params.workspaceDir);
+  const files = await listMemoryFiles(params.workspaceDir, params.additionalPaths);
   const fileEntries = await Promise.all(
     files.map(async (file) => buildFileEntry(file, params.workspaceDir)),
   );