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/writeGuide.ts

@@ -0,0 +1,30 @@
+import { tool } from 'ai';
+import { z } from 'zod';
+import { writeGuide } from '@/services/guides/guideService';
+import { eventBroadcaster } from '@/services/events';
+
+export const writeGuideTool = tool({
+  description: 'Write or update a guide. Content should be full markdown with YAML frontmatter (name, description).',
+  inputSchema: z.object({
+    name: z.string().describe('The name of the guide to write'),
+    content: z.string().describe('Full markdown content including YAML frontmatter'),
+  }),
+  execute: async ({ name, content }) => {
+    try {
+      writeGuide(name, content);
+      eventBroadcaster.broadcast({ type: 'GUIDE_UPDATED', data: { name } });
+      return {
+        success: true,
+        data: { name },
+        message: `Guide "${name}" saved`,
+      };
+    } catch (error) {
+      console.error('[writeGuide] error:', error);
+      return {
+        success: false,
+        error: error instanceof Error ? error.message : 'Failed to write guide',
+        data: null,
+      };
+    }
+  },
+});