feat: MCP server v1.2.0 — guide system + read/write guide tools

Adds full guide system to MCP standalone server. System guides (schema,
creating-nodes, edges, dimensions, extract) are bundled and immutable.
Users can create up to 10 custom guides via rah_write_guide. Syncs guide
infrastructure from main repo to OS repo app code.

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

apps/mcp-server-standalone/guides/system/extract.md

@@ -0,0 +1,33 @@
+---
+name: Extract
+description: Extraction pre-check. When to reuse chunks vs re-extract.
+immutable: true
+---
+
+# Content Extraction
+
+## Pre-Check (REQUIRED)
+
+Before running any extraction tool, always check the node first:
+
+1. Call `getNodesById` on the target node
+2. Check `chunk_status`:
+   - **'chunked'** → content already extracted. Reuse existing chunks. Do NOT re-extract.
+   - **'pending'** or missing → safe to extract
+   - **'failed'** → previous extraction failed, safe to retry
+
+3. Check if embeddings are available (chunk length > 0)
+   - If available, use `searchContentEmbeddings` instead of re-extracting
+
+## Extraction Tools
+
+- **youtubeExtract** — YouTube videos (requires URL with video ID)
+- **websiteExtract** — Web pages (uses Jina.ai for JS-rendered sites)
+- **paperExtract** — PDF files (requires direct PDF URL)
+
+## After Extraction
+
+- The extracted content goes into `chunk` (full source)
+- AI generates a `description` (grounding summary)
+- Embeddings are created automatically
+- Assign to relevant dimensions