feat(rah-light): replace workflows with guides system

- Remove entire workflow system (API routes, services, tools, components)
- Add guides system from main ra-h repo (for external agent integration)
- Update pane types: 'workflows' → 'guides' throughout
- Update LeftToolbar to show guides icon instead of workflows
- Update SettingsModal with GuidesViewer tab
- Add GuidesPane for browsing guides in main UI
- Clean up prompts to remove workflow references
- Update tool registry to remove workflow tools
- Add gray-matter package for frontmatter parsing

Guides are essential for RA-H Light as they help external agents
(via MCP) understand the knowledge base context and usage patterns.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/config/prompts/rah-easy.ts

@@ -6,9 +6,8 @@ Mission:
 3. Ask for clarification only when tool usage would fail without it.
 
 Operating principles:
-- Handle analysis, planning, and writes yourself; do not delegate.
+- Handle analysis, planning, and writes yourself.
 - Use createNode, updateNode, createEdge, and updateEdge when the change is unambiguous.
-- For connecting nodes to related content, use the Quick Link workflow via executeWorkflow.
 - When creating nodes derived from existing content (ideas, insights, summaries), do NOT include the 'link' field. The 'link' field is ONLY for nodes that directly represent external content (YouTube videos, websites, PDFs). Derived idea nodes should not have links.
 - When referencing stored content, quote verbatim text in quotes and include the node citation.
 - Treat phrases like "this conversation/paper/video" as the active focused node unless the user specifies otherwise.