feat(rag): lite-model document summaries — non-markdown docs summarized at import, summary chunk retrieves and resolves to the full source doc

alembic/versions/0004_summary_columns.py

@@ -0,0 +1,45 @@
+"""document summaries: documents.summary + chunks.is_summary
+
+Revision ID: 0004
+Revises: 0003
+Create Date: 2026-08-25
+
+Phase 30 (document-summaries story, A13 — two additive, reversible
+columns, no table rework):
+
+* ``documents.summary`` — TEXT, nullable. Natural-language summary of the
+  document produced at import time by the aipi ``lite`` model (non-markdown
+  A9 documents only). NULL for markdown docs and for documents imported
+  before summaries existed (or whose summary generation failed — the
+  fail-soft path still indexes the document without a summary).
+* ``chunks.is_summary`` — BOOLEAN NOT NULL DEFAULT false. Marks the single
+  extra summary chunk (position -1) that mirrors ``documents.summary`` into
+  the embedding space, so hybrid search has a well-embedding
+  natural-language target for badly-formatted raw text. The default keeps
+  every pre-0004 row valid; the summary chunk flows through the unchanged
+  A7 retrieval path (cosine ∪ FTS ∪ RRF) and the existing chunk→document
+  mapping resolves a summary hit to its full source document.
+"""
+from __future__ import annotations
+
+import sqlalchemy as sa
+
+from alembic import op
+
+revision = "0004"
+down_revision = "0003"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("documents", sa.Column("summary", sa.Text(), nullable=True))
+    op.add_column(
+        "chunks",
+        sa.Column("is_summary", sa.Boolean(), nullable=False, server_default=sa.text("false")),
+    )
+
+
+def downgrade() -> None:
+    op.drop_column("chunks", "is_summary")
+    op.drop_column("documents", "summary")