Merges FN-5218: adds hash mention support (`#`) in chat composers, grouping task and file reference results in a unified popup, with wiring into `ChatView` and `QuickChatFAB`, plus test coverage and docs. The hook `useFileMention` is extended and refactored, and the file mention popup UI is updated
Fusion-Task-Id: FN-5218
This merge introduces SWR-style caching across the dashboard to eliminate redundant fetches for models, agents, and skills, significantly refactoring ChatView.tsx (reduced by ~140 lines) by offloading cache coordination to three new dedicated hooks (`useAgentsMapCache`, `useDiscoveredSkillsCache`, `
Fusion-Task-Id: FN-5202
