fix(FN-915): use getFusionDir() for agent storage location

- Add getFusionDir() method to TaskStore for resolving agent database path
- Update in-process-runtime to use getFusionDir() instead of hardcoded path
- Update dashboard routes AgentStore initialization to use getFusionDir()
- Add changeset for published package patch bump

.changeset/fn-915-agents-under-fusion.md

@@ -0,0 +1,5 @@
+---
+"@gsxdsm/fusion": patch
+---
+
+Fix agent storage location: agents are now saved under `.fusion/agents/` instead of the project root `/agents/` directory.