feat(chat): invalidate saved chats on sources sync — versioned stamps, stale marker, Regenerate against the new index

tests/integration/test_sync_api.py

@@ -39,6 +39,15 @@ real ``LLMClient`` the probe is stubbed (:func:`_stub_probe`) so no
 test ever hits the network; the ``_real_llm`` tests get a passing
 probe from ``FakeEmbedder.embed_one``/``chat``.
 
+Phase 53 (task 02): the sources-version bump — a sync whose import
+changed the KB (added + updated + pruned > 0) advances the single-row
+``sources_meta`` counter exactly once (the new generation lands in the
+``/api/sync/status`` detail as ``sources_version``); an unchanged
+re-sync never bumps (the detail still reports the current generation),
+and every failure path (git error, model down) never bumps. The
+counter is pinned to the migration-0010 seed (0) around every test by
+:func:`_reset_sources_version`.
+
 The git / import / overview layers are monkeypatched in ``app.api.sync``
 (same fake style as ``test_import_docs_git.py``) — no real git, no LLM:
 the runner's state machine and HTTP surface are under test.
@@ -66,11 +75,13 @@ from sqlalchemy.orm import Session
 
 from app.api import sync as sync_api
 from app.config import Settings
+from app.db import SessionLocal, db_available
 from app.main import app as fastapi_app
 from app.models import GitSource
 from app.rag import git_sources as git_sources_resolver
 from app.rag.importer import ImportSummary
 from app.rag.llm import EmbeddingError, LLMClient, ModelUnavailableError
+from app.rag.sources_meta import current_sources_version
 from scripts.git_sync import GitSyncError
 from tests.conftest import ADMIN_PASSWORD
 from tests.fakes import FakeEmbedder
@@ -100,6 +111,26 @@ def clean_git_sources(db: Session) -> Iterator[None]:
     db.commit()
 
 
+@pytest.fixture(autouse=True)
+def _reset_sources_version() -> Iterator[None]:
+    """Phase 53: the sources version counter is global mutable state —
+    pin it to the migration-0010 seed (0) around every sync test so the
+    bump assertions start from a known generation (own session: the
+    runner bumps through its own short-lived ``SessionLocal``).
+    Skips like the ``db`` fixture when Postgres is down."""
+    if not db_available():
+        pytest.skip("Postgres not reachable — run `podman compose up -d db` first")
+    session = SessionLocal()
+    try:
+        session.execute(text("UPDATE sources_meta SET version = 0 WHERE id = 1"))
+        session.commit()
+        yield
+    finally:
+        session.execute(text("UPDATE sources_meta SET version = 0 WHERE id = 1"))
+        session.commit()
+        session.close()
+
+
 @pytest.fixture()
 def sync_client() -> Iterator[TestClient]:
     """Context-managed TestClient — one app event loop across requests
@@ -310,7 +341,10 @@ def test_admin_sync_success_reports_full_detail(
         "files": 5, "added": 1, "updated": 2, "unchanged": 2, "pruned": 3,
         "errors": 0, "chunks": 11, "summaries": 1, "summary_errors": 0,
         "overview": True,
+        "sources_version": 1,  # phase 53: changed KB → exactly one bump (0 → 1)
     }
+    # The bump committed: the counter advanced exactly once, not twice.
+    assert current_sources_version(db) == 1
     # Git: the configured repo was cloned into BOR_SOURCES_DIR/<repo-name>/.
     assert clone_calls == [(repo_url, tmp_path / "bor" / "repo")]
     # Import: exactly the checkouts, with prune=True (the button is the
@@ -354,6 +388,10 @@ def test_unchanged_kb_skips_overview_refresh(
     assert body["detail"]["overview"] is False
     assert fake_overview.llms == []  # no wasted model call
     assert len(fake_import.llms) == 1  # the import itself ran
+    # Phase 53: an unchanged re-sync never bumps — the detail reports
+    # the current (unadvanced) generation.
+    assert body["detail"]["sources_version"] == 0
+    assert current_sources_version(db) == 0
 
 
 # --- admin: concurrency ----------------------------------------------------
@@ -435,6 +473,8 @@ def test_git_failure_marks_failed_and_skips_import(
     assert body["finished_at"] is not None
     assert fake_import.sources == []  # no partial import
     assert fake_overview.llms == []
+    # Phase 53: a FAILED sync never bumps — the version is untouched.
+    assert current_sources_version(db) == 0
 
     # A failed run leaves the system restartable: a new POST is accepted.
     assert sync_client.post("/api/sync").status_code == 202
@@ -773,6 +813,8 @@ def test_model_down_fails_fast_before_any_clone(
     assert body["detail"] == {}
     assert clone_calls == []  # fail fast: before any clone
     assert fake_import.sources == []  # and before any import
+    # Phase 53: a FAILED sync (model down) never bumps.
+    assert current_sources_version(db) == 0
 
 
 def test_probe_names_dead_embed_model_and_masks_credentials(