fix: mermaid preview rendering + useShallow infinite loop

[aterrylu]

Summary

• Mermaid rendering fixed — diagrams in markdown preview now render correctly with error handling
• React chore(release): version packages #185 hotfix — fixes infinite re-render loop from perf PR's useSidebarActions() missing useShallow

Problem

1. Mermaid code blocks in markdown previews silently rendered nothing — mermaid.render() had no .catch(), useId() caused StrictMode ID collisions, and react-markdown v10 passes children as React nodes not strings
2. Perf PR (perf: Tier 1 dashboard rendering optimizations #88) introduced a useSidebarActions() selector that returned a new {} on every store update without useShallow, causing infinite re-renders (React error chore(release): version packages #185 on page load)

Changes

Fix	File	Issue
Add .catch() to mermaid.render	PreviewPane.tsx, PreviewPage.tsx	Silent failures → visible error
Monotonic counter for diagram IDs	Both preview files	StrictMode double-render collisions
Coerce children to string	Both preview files	react-markdown v10 compatibility
Add useShallow to useSidebarActions	Sidebar.tsx	Infinite re-render loop

Test plan

• Dashboard loads without React error chore(release): version packages #185
• Deployed and verified on forge
• Open markdown file with mermaid code block — should render diagram
• Invalid mermaid syntax shows error message (not blank)

🤖 Generated with Claude Code