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/tools/guides/readGuide.ts

@@ -0,0 +1,34 @@
+import { tool } from 'ai';
+import { z } from 'zod';
+import { readGuide } from '@/services/guides/guideService';
+
+export const readGuideTool = tool({
+  description: 'Read a guide by name. Returns the full markdown content with instructions.',
+  inputSchema: z.object({
+    name: z.string().describe('The name of the guide to read'),
+  }),
+  execute: async ({ name }) => {
+    try {
+      const guide = readGuide(name);
+      if (!guide) {
+        return {
+          success: false,
+          error: `Guide "${name}" not found`,
+          data: null,
+        };
+      }
+      return {
+        success: true,
+        data: guide,
+        message: `Loaded guide: ${guide.name}`,
+      };
+    } catch (error) {
+      console.error('[readGuide] error:', error);
+      return {
+        success: false,
+        error: error instanceof Error ? error.message : 'Failed to read guide',
+        data: null,
+      };
+    }
+  },
+});