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/config/schema.ts

@@ -222,6 +222,7 @@ const FIELD_LABELS: Record<string, string> = {
   "agents.defaults.memorySearch": "Memory Search",
   "agents.defaults.memorySearch.enabled": "Enable Memory Search",
   "agents.defaults.memorySearch.sources": "Memory Search Sources",
+  "agents.defaults.memorySearch.paths": "Additional Memory Paths",
   "agents.defaults.memorySearch.experimental.sessionMemory":
     "Memory Search Session Index (Experimental)",
   "agents.defaults.memorySearch.provider": "Memory Search Provider",
@@ -499,6 +500,8 @@ const FIELD_HELP: Record<string, string> = {
     "Vector search over MEMORY.md and memory/*.md (per-agent overrides supported).",
   "agents.defaults.memorySearch.sources":
     'Sources to index for memory search (default: ["memory"]; add "sessions" to include session transcripts).',
+  "agents.defaults.memorySearch.paths":
+    "Additional paths to include in memory search (directories or .md files; relative paths resolved from workspace).",
   "agents.defaults.memorySearch.experimental.sessionMemory":
     "Enable experimental session transcript indexing for memory search (default: false).",
   "agents.defaults.memorySearch.provider": 'Embedding provider ("openai", "gemini", or "local").',