feat: port source-first ingestion to os repo

- make source the canonical field across os routes, tools, ui, and mcp
- align fresh-install schema, search, and embedding flows with source-first ingestion

Generated with Claude Code

app/api/extract/pdf/upload/route.ts

@@ -57,10 +57,8 @@ export async function POST(request: NextRequest) {
       headers: { 'Content-Type': 'application/json' },
       body: JSON.stringify({
         title,
-        // Give the description generator and UI a readable summary plus a short excerpt.
-        notes: `Imported PDF document: ${file.name} (${extraction.metadata.pages} pages, ${Math.round(extraction.metadata.text_length / 1000)}k characters).\n\nPreview:\n${extraction.chunk.slice(0, 1200)}`,
-        // Full extracted text goes in chunk for universal chunking/embedding
-        chunk: extraction.chunk,
+        description: `PDF document imported from ${file.name} — ${extraction.metadata.pages} pages of extracted text. Useful as a searchable local source.`,
+        source: extraction.chunk,
         metadata: {
           source: 'pdf_upload',
           original_filename: file.name,