feat(pdf): improve download filename with company names and date

- Generate descriptive filenames: swot-{company}-vs-{competitor}-{date}.pdf
- Sanitize company names for filesystem safety
- Include date in YYYY-MM-DD format
- Handle multiple comparison entities (e.g., "plus2" for 2 additional)

Examples:
- Single entity: "swot-Apple-2026-02-04.pdf"
- With comparison: "swot-Apple-vs-Microsoft-2026-02-04.pdf"
- Multiple comparisons: "swot-Apple-vs-Microsoft-plus2-2026-02-04.pdf"

Fixes: Downloaded PDF had generic filename with .txt suffix

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

src/backend/site/router.py

@@ -218,8 +218,35 @@ async def download_pdf(request: Request) -> StreamingResponse:
         # Cache the generated PDF
         pdf_cache.set(session_id, result, pdf_buffer)
 
-    # Prepare filename
-    filename = f"swot-analysis-{session_id[:8]}.pdf"
+    # Prepare filename with company names and date
+    import re
+    from datetime import datetime
+
+    # Sanitize company names for filename (remove special chars, limit length)
+    def sanitize_filename(text: str, max_length: int = 30) -> str:
+        # Remove special characters, keep alphanumeric, spaces, hyphens
+        text = re.sub(r"[^\w\s-]", "", text)
+        # Replace spaces with hyphens
+        text = re.sub(r"\s+", "-", text.strip())
+        # Limit length
+        return text[:max_length].rstrip("-")
+
+    # Build entity string
+    primary = sanitize_filename(result.primary_entity)
+    if result.comparison_entities:
+        # Include first comparison entity
+        comparison = sanitize_filename(result.comparison_entities[0])
+        entities_str = f"{primary}-vs-{comparison}"
+        if len(result.comparison_entities) > 1:
+            entities_str += f"-plus{len(result.comparison_entities) - 1}"
+    else:
+        entities_str = primary
+
+    # Add date
+    date_str = datetime.now().strftime("%Y-%m-%d")
+
+    # Build final filename
+    filename = f"swot-{entities_str}-{date_str}.pdf"
 
     # Return as streaming response (iterate over BytesIO in chunks)
     def iterfile():
@@ -230,7 +257,7 @@ async def download_pdf(request: Request) -> StreamingResponse:
         content=iterfile(),
         media_type="application/pdf",
         headers={
-            "Content-Disposition": f"attachment; filename={filename}",
+            "Content-Disposition": f'attachment; filename="{filename}"',
             "Cache-Control": "no-cache",
         },
     )

tests/integration/test_pdf_export.py

@@ -230,7 +230,9 @@ class TestPDFDownloadEndpoint:
         assert response.status_code == 200
         assert response.headers["content-type"] == "application/pdf"
         assert "attachment" in response.headers["content-disposition"]
-        assert "swot-analysis" in response.headers["content-disposition"]
+        # New filename format: swot-{company}-{date}.pdf
+        assert "swot-" in response.headers["content-disposition"]
+        assert ".pdf" in response.headers["content-disposition"]
 
         # Verify it's a valid PDF by reading the stream
         body_content = b""
@@ -281,7 +283,9 @@ class TestPDFDownloadEndpoint:
     async def test_download_pdf_filename_format(
         self, mock_session_id: str, sample_swot_analysis
     ):
-        """Test PDF filename follows expected format"""
+        """Test PDF filename follows expected format: swot-{company}-{date}.pdf"""
+        from datetime import datetime
+
         from backend.site.router import download_pdf
 
         # Create mock request
@@ -297,5 +301,10 @@ class TestPDFDownloadEndpoint:
 
         assert response.status_code == 200
         disposition = response.headers["content-disposition"]
-        # Format: swot-analysis-{session_id[:8]}.pdf
-        assert f"swot-analysis-{mock_session_id[:8]}.pdf" in disposition
+
+        # New format: swot-{primary_entity}-vs-{comparison[0]}-{date}.pdf
+        # Sample has primary_entity="Google", comparison_entities=["Microsoft", "Amazon"]
+        assert "swot-Google-vs-Microsoft" in disposition
+        assert "plus1" in disposition  # +1 more comparison (Amazon)
+        assert datetime.now().strftime("%Y-%m-%d") in disposition
+        assert ".pdf" in disposition