fix(documents): restore PDF library metadata and preview (#2483)

PDF uploads are stored as markdown wrappers with pdf_source or pdf_form_source markers so the editor can preserve extracted text, form fields, and annotations. The library exposed that internal wrapper: auto-created PDF documents used the hashed storage filename as the title, and row/facet language reported markdown instead of pdf.

Derive chat-upload PDF titles from the original upload name, derive document-library display language from the PDF source marker for rows, filters, and facets, and keep markdown wrappers excluded from the markdown facet when they represent PDFs.

The expanded library card already renders PDF-backed documents through /api/document/{id}/render-pdf. Allow only that inline PDF preview endpoint to be framed by same-origin app pages while leaving normal routes on X-Frame-Options: DENY and frame-ancestors none.

Also tighten the existing PDF marker regression assertion so it matches the actual historical corruption signature instead of contradicting the preserved [Page 1 text]: marker.

Fixes #2468

routes/document_routes.py

@@ -7,7 +7,7 @@ from typing import Dict, Any, List, Optional
 
 from fastapi import APIRouter, HTTPException, Query, Request, UploadFile, File, Form
 
-from sqlalchemy import func, or_
+from sqlalchemy import case, func, or_
 from core.database import SessionLocal, Document, DocumentVersion
 from core.database import Session as DbSession
 from src.auth_helpers import get_current_user
@@ -39,6 +39,19 @@ def _aggregate_language_facets(lang_rows):
     return out
 
 
+def _library_language_for_document(doc: Document) -> str:
+    """Return the display language used by the document library.
+
+    PDF documents are stored as markdown wrappers so the editor can preserve
+    extracted text, form fields, and annotations. The library should still
+    identify them as PDFs instead of exposing that internal wrapper format.
+    """
+    from src.pdf_form_doc import find_source_upload_id
+
+    if find_source_upload_id(doc.current_content or ""):
+        return "pdf"
+    return doc.language or "text"
+
 
 from routes.document_helpers import (
     DocumentCreate, DocumentUpdate, DocumentPatch,
@@ -260,18 +273,29 @@ def setup_document_routes(session_manager, upload_handler=None) -> APIRouter:
         db = SessionLocal()
         try:
             from sqlalchemy import or_
+            pdf_marker_cond = or_(
+                Document.current_content.like('%<!-- pdf_source upload_id="%'),
+                Document.current_content.like('%<!-- pdf_form_source upload_id="%'),
+            )
+            library_language_expr = case(
+                (pdf_marker_cond, "pdf"),
+                (Document.language.is_(None), "text"),
+                else_=Document.language,
+            )
             # Archived view shows ONLY archived docs; the default view excludes
             # them (NULL = legacy rows that predate the column = not archived).
             _arch_cond = (Document.archived == True) if archived else or_(
                 Document.archived == False, Document.archived.is_(None))
-            # Language facet counts (owner-filtered)
+            # Language facet counts (owner-filtered). PDF documents are stored
+            # as markdown wrappers, so group by the library display language
+            # instead of the raw stored language.
             lang_q = (
-                db.query(Document.language, func.count(Document.id))
+                db.query(library_language_expr, func.count(Document.id))
                 .outerjoin(DbSession, Document.session_id == DbSession.id)
                 .filter(Document.is_active == True).filter(_arch_cond)
             )
             lang_q = _owner_session_filter(lang_q, user)
-            lang_rows = lang_q.group_by(Document.language).all()
+            lang_rows = lang_q.group_by(library_language_expr).all()
             languages = _aggregate_language_facets(lang_rows)
 
             # Session count (owner-filtered)
@@ -303,12 +327,17 @@ def setup_document_routes(session_manager, upload_handler=None) -> APIRouter:
                         Document.title.ilike(term) | Document.current_content.ilike(term)
                     )
 
-            # Language filter
+            # Language filter. "pdf" is a display language derived from the
+            # source marker; "markdown" excludes those wrappers.
             if language:
                 if language == "text":
                     q = q.filter((Document.language == None) | (Document.language == "text"))
+                elif language == "pdf":
+                    q = q.filter(pdf_marker_cond)
                 else:
                     q = q.filter(Document.language == language)
+                    if language == "markdown":
+                        q = q.filter(~pdf_marker_cond)
 
             # Total before pagination
             total = q.count()
@@ -332,7 +361,7 @@ def setup_document_routes(session_manager, upload_handler=None) -> APIRouter:
                     "session_id": doc.session_id,
                     "session_name": session_name,
                     "title": doc.title,
-                    "language": doc.language or "text",
+                    "language": _library_language_for_document(doc),
                     "preview": (doc.current_content or "")[:500],
                     "version_count": doc.version_count,
                     "created_at": (doc.created_at.isoformat() + "Z") if doc.created_at else None,