* feat(chat): add mermaid preview popups and fullscreen diagram viewer
Enable opening Mermaid diagrams from markdown and file attachments with a dedicated fullscreen dialog, while tightening preview loading behavior and sizing for more reliable interaction.
* refactor(chat): extract shared preview overlay hooks
Centralize fullscreen preview transition and viewport lifecycle logic so image and Mermaid dialogs stay behaviorally aligned while reducing maintenance overhead.
* fix(security): enforce workspace boundaries for fs read endpoints
Validate /api/fs/read and /api/fs/raw paths against active workspace roots and canonical realpaths to block traversal and symlink escapes before serving file contents.
* fix(chat): remove dead Mermaid copy component
Drop an unused merge-leftover component in MarkdownRenderer to keep lint clean without changing Mermaid preview behavior.
Iuliia Ivashko
d2d39c48ac