Overhaul docs retrieval and web search quality

Replace the abandoned llms-txt-mcp/Chroma docs backend with an in-repo
MCP service: SQLite WAL + FTS5 + sentence-transformer embeddings,
transactional source replacement, persisted state across restarts,
singleflight refresh with conditional requests, hybrid lexical/semantic
ranking with exact-duplicate collapse, source/host filters, and
explicit-by-default content retrieval. Add docs_rebuild and a
docs-rebuild CLI command.

Add deterministic llms-full.txt snapshot generation for machine-local
menus with hash-validated provenance manifests; lifecycle commands
promote a local menu to its snapshot only when the manifest validates.
Switch public source profiles to content-bearing llms-full.txt feeds.

Improve web search: bounded provider fallback with per-attempt
diagnostics and cancellation, an optional Brave Search API provider,
strict SearXNG engine selection, capped link/media extraction, and a
real engine=browser renderer that routes every request through the
existing SSRF vetting while blocking WebSockets, non-GET traffic, and
private destinations.

Extend release checks with offline unit suites and isolated candidate
container tests for both images.

docker/docs/tests/test_store.py

@@ -0,0 +1,99 @@
+from __future__ import annotations
+
+import tempfile
+import unittest
+from pathlib import Path
+
+import numpy as np
+
+from context_docs.models import PreparedDocument, SourceUpdate
+from context_docs.store import IndexStore
+
+
+def document(identifier: str, source: str, title: str, content: str) -> PreparedDocument:
+    return PreparedDocument(
+        id=identifier,
+        configured_source=source,
+        resolved_source=source,
+        source_host="example.test",
+        canonical_url=f"https://docs.example.test/{identifier}",
+        canonical_host="docs.example.test",
+        title=title,
+        description="",
+        heading_path=title,
+        content=content,
+        content_hash=identifier,
+        embedding=np.asarray([1.0, 0.0, 0.0, 0.0], dtype=np.float32),
+    )
+
+
+def update(source: str, documents: list[PreparedDocument], checked_at: float = 100.0) -> SourceUpdate:
+    return SourceUpdate(
+        configured_source=source,
+        resolved_source=source,
+        etag=None,
+        last_modified=None,
+        body_hash="body-hash",
+        raw_body="# Fixture",
+        parser_fingerprint="parser-v1",
+        embedding_fingerprint="fake-embedder-v1",
+        checked_at=checked_at,
+        indexed_at=checked_at,
+        stale_at=checked_at + 3600,
+        documents=documents,
+    )
+
+
+class StoreTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.tmp = tempfile.TemporaryDirectory()
+        self.path = Path(self.tmp.name) / "docs.sqlite3"
+        self.source = "https://example.test/llms.txt"
+        self.store = IndexStore(self.path)
+        self.store.configure_sources([self.source])
+
+    def tearDown(self) -> None:
+        self.store.close()
+        self.tmp.cleanup()
+
+    def test_replacement_removes_old_only_documents(self) -> None:
+        self.store.replace_source(update(self.source, [document("old", self.source, "Old", "old content")]))
+        self.store.replace_source(update(self.source, [document("new", self.source, "New", "new content")]))
+
+        self.assertIsNone(self.store.get_document("old"))
+        self.assertEqual("new content", self.store.get_document("new").content)
+
+    def test_failed_replacement_rolls_back_to_previous_generation(self) -> None:
+        self.store.replace_source(update(self.source, [document("old", self.source, "Old", "old content")]))
+        self.store.connection.execute(
+            "CREATE TRIGGER reject_failure BEFORE INSERT ON documents "
+            "WHEN NEW.title = 'FAIL' BEGIN SELECT RAISE(ABORT, 'injected failure'); END"
+        )
+
+        with self.assertRaisesRegex(Exception, "injected failure"):
+            self.store.replace_source(update(self.source, [document("bad", self.source, "FAIL", "bad")]))
+
+        self.assertEqual("old content", self.store.get_document("old").content)
+        self.assertIsNone(self.store.get_document("bad"))
+
+    def test_restart_loads_persisted_state_without_network(self) -> None:
+        self.store.replace_source(update(self.source, [document("persisted", self.source, "Persisted", "saved")]))
+        self.store.close()
+
+        self.store = IndexStore(self.path)
+        self.store.configure_sources([self.source])
+
+        states = self.store.list_sources()
+        self.assertEqual(1, states[0].doc_count)
+        self.assertEqual("saved", self.store.get_document("persisted").content)
+
+    def test_removed_source_is_not_searchable_or_retrievable(self) -> None:
+        self.store.replace_source(update(self.source, [document("retired", self.source, "Retired", "identifier")]))
+        self.store.configure_sources([])
+
+        self.assertIsNone(self.store.get_document("retired"))
+        self.assertEqual([], self.store.lexical_search("identifier", limit=5))
+
+
+if __name__ == "__main__":
+    unittest.main()