feat(viewer): show document summary together with the original (TODO.md L5)

app/schemas.py

@@ -105,6 +105,10 @@ class DocContent(BaseModel):
     path: str
     title: str
     format: str
+    #: Lite-model summary (phase 30) — non-markdown A9 docs only; None for
+    #: markdown documents, pre-phase-30 rows, and the fail-soft path where
+    #: summary generation failed but the document was still indexed.
+    summary: str | None = None
     content: str
     indexed_at: str
     chunks: int