Filter private knowledge before applying shared result limits

Why:
Higher-ranked private rows could exhaust SQL candidate limits and hide an
otherwise authorized published slice from a member's current-project search.

Evidence:
SELF TestAuthorizedKnowledgeFiltersBeforeTopK failed with no shared hits before
the change and passed after it. SELF go test ./... and the isolated PostgreSQL
Store suite passed; independent replay and current-HEAD CI remain owner gates.

Impact:
Scan the resource-authorized shared fulltext path until enough allowed results
are found. Preserve ordinary legacy retrieval candidate limits and semantics.

Refs:
Dev project-member-access plan r1 Task 1; R5 published knowledge availability

internal/store/content.go

@@ -381,7 +381,11 @@ func sharedVisible(requester string, q core.RetrievalQuery, allow func(docOwner,
 // 经 allow(docOwner, projectID) 放行的命中（全文通道；向量通道共享仍留后续切片）。
 // allow 出错由调用方前置处理——本层只见布尔。
 func (s *Store) SearchKnowledgeShared(requester string, q core.RetrievalQuery, allow func(docOwner, projectID core.ID) bool) ([]core.RetrievalHit, error) {
-	return s.SearchKnowledgeSharedAuthorized(requester, q, func(d core.KnowledgeDoc) bool { return allow(d.Owner, d.ProjectID) })
+	pred := sharedVisible(requester, q, allow)
+	if s.dialect.name() == "postgres" {
+		return s.searchKnowledgePGShared(requester, q, pred)
+	}
+	return s.searchKnowledgeSQLiteShared(requester, q, pred)
 }
 
 // SearchKnowledgeSharedAuthorized evaluates the trusted document identity before
@@ -393,9 +397,16 @@ func (s *Store) SearchKnowledgeSharedAuthorized(requester string, q core.Retriev
 			(len(q.Sources) == 0 || containsStr(q.Sources, d.Source)) && allow(d)
 	}
 	if s.dialect.name() == "postgres" {
-		return s.searchKnowledgePGShared(requester, q, pred)
+		return s.searchKnowledgePGSharedCandidates(requester, q, pred, false)
 	}
-	return s.searchKnowledgeSQLiteShared(requester, q, pred)
+	out, err := s.searchKnowledgeFTSCandidates(pred, q, false)
+	if err != nil {
+		return nil, err
+	}
+	if len(out) == 0 && q.Text != "" {
+		return s.searchKnowledgeLikeSharedCandidates(requester, q, pred, false)
+	}
+	return out, nil
 }
 
 // DeleteProjectKnowledgeByRef replaces one publication scope and its vectors in
@@ -452,14 +463,23 @@ func (s *Store) searchKnowledgeSQLiteShared(requester string, q core.RetrievalQu
 
 // searchKnowledgeFTS FTS 通道（owner 作用域与共享作用域共用：可见性谓词由调用方注入）。
 func (s *Store) searchKnowledgeFTS(pred knowledgePred, q core.RetrievalQuery) ([]core.RetrievalHit, error) {
+	return s.searchKnowledgeFTSCandidates(pred, q, true)
+}
+
+func (s *Store) searchKnowledgeFTSCandidates(pred knowledgePred, q core.RetrievalQuery, bounded bool) ([]core.RetrievalHit, error) {
 	topK := q.TopK
 	if topK <= 0 {
 		topK = 5
 	}
-	rows, err := s.db.Query(s.q(`
-		SELECT k.id,k.owner,k.project_id,k.source,k.title,k.ref,k.chunk,k.created_at, rank
-		FROM knowledge_fts f JOIN knowledge k ON k.rowid=f.rowid
-		WHERE knowledge_fts MATCH ? ORDER BY rank LIMIT ?`), ftsQuery(q.Text), topK*2)
+	query := `SELECT k.id,k.owner,k.project_id,k.source,k.title,k.ref,k.chunk,k.created_at, rank
+        FROM knowledge_fts f JOIN knowledge k ON k.rowid=f.rowid
+        WHERE knowledge_fts MATCH ? ORDER BY rank`
+	args := []any{ftsQuery(q.Text)}
+	if bounded {
+		query += " LIMIT ?"
+		args = append(args, topK*2)
+	}
+	rows, err := s.db.Query(s.q(query), args...)
 	if err != nil {
 		return nil, err
 	}
@@ -482,12 +502,21 @@ func (s *Store) searchKnowledgeFTS(pred knowledgePred, q core.RetrievalQuery) ([
 }
 
 func (s *Store) searchKnowledgeLikeShared(requester string, q core.RetrievalQuery, pred knowledgePred) ([]core.RetrievalHit, error) {
+	return s.searchKnowledgeLikeSharedCandidates(requester, q, pred, true)
+}
+
+func (s *Store) searchKnowledgeLikeSharedCandidates(requester string, q core.RetrievalQuery, pred knowledgePred, bounded bool) ([]core.RetrievalHit, error) {
 	topK := q.TopK
 	if topK <= 0 {
 		topK = 5
 	}
-	rows, err := s.db.Query(s.q(`SELECT id,owner,project_id,source,title,ref,chunk,created_at FROM knowledge WHERE owner<>? AND owner<>'' AND (chunk LIKE ? OR title LIKE ?) LIMIT ?`),
-		requester, "%"+q.Text+"%", "%"+q.Text+"%", topK)
+	query := `SELECT id,owner,project_id,source,title,ref,chunk,created_at FROM knowledge WHERE owner<>? AND owner<>'' AND (chunk LIKE ? OR title LIKE ?)`
+	args := []any{requester, "%" + q.Text + "%", "%" + q.Text + "%"}
+	if bounded {
+		query += " LIMIT ?"
+		args = append(args, topK)
+	}
+	rows, err := s.db.Query(s.q(query), args...)
 	if err != nil {
 		return nil, err
 	}

internal/store/knowledge_authorization_test.go

@@ -0,0 +1,22 @@
+package store
+
+import (
+	core "agent-system-core"
+	"testing"
+)
+
+func TestAuthorizedKnowledgeFiltersBeforeTopK(t *testing.T) {
+	st := openTestStore(t)
+	docs := []core.KnowledgeDoc{}
+	for i := 0; i < 20; i++ {
+		docs = append(docs, core.KnowledgeDoc{Owner: "alice", ProjectID: "domain", Source: "private", Chunk: "sharedterm sharedterm sharedterm sharedterm"})
+	}
+	docs = append(docs, core.KnowledgeDoc{ID: "published", Owner: "alice", ProjectID: "domain", Source: "plugin:rdm:published", Chunk: "sharedterm plus additional explanatory words for this lower scoring published source"})
+	if err := st.AddKnowledge(docs...); err != nil {
+		t.Fatal(err)
+	}
+	hits, err := st.SearchKnowledgeSharedAuthorized("bob", core.RetrievalQuery{Text: "sharedterm", ProjectID: "domain", TopK: 1}, func(d core.KnowledgeDoc) bool { return d.ID == "published" })
+	if err != nil || len(hits) != 1 || hits[0].Doc.ID != "published" {
+		t.Fatalf("denied rows consumed top-k: %+v %v", hits, err)
+	}
+}

internal/store/search_postgres.go

@@ -53,19 +53,28 @@ func (s *Store) searchKnowledgePG(owner string, q core.RetrievalQuery) ([]core.R
 // searchKnowledgePGShared EXT-8 切片 2 共享版：他人 owner 的行 + 谓词后置判定
 // （allow 回调由上层注入；排序与自检索同构）。
 func (s *Store) searchKnowledgePGShared(requester string, q core.RetrievalQuery, pred knowledgePred) ([]core.RetrievalHit, error) {
+	return s.searchKnowledgePGSharedCandidates(requester, q, pred, true)
+}
+
+func (s *Store) searchKnowledgePGSharedCandidates(requester string, q core.RetrievalQuery, pred knowledgePred, bounded bool) ([]core.RetrievalHit, error) {
 	topK := q.TopK
 	if topK <= 0 {
 		topK = 5
 	}
 	text := q.Text
-	rows, err := s.db.Query(s.q(`
+	query := `
 		SELECT k.id,k.owner,k.project_id,k.source,k.title,k.ref,k.chunk,k.created_at,
 		       ts_rank(k.tsv, websearch_to_tsquery('simple', ?)) AS r
 		FROM knowledge k
 		WHERE (k.owner<>? AND k.owner<>'')
 		  AND (? = '' OR k.tsv @@ websearch_to_tsquery('simple', ?) OR k.chunk LIKE ? OR k.title LIKE ?)
-		ORDER BY r DESC, k.created_at DESC
-		LIMIT ?`), text, requester, text, text, "%"+text+"%", "%"+text+"%", topK*2)
+		ORDER BY r DESC, k.created_at DESC`
+	args := []any{text, requester, text, text, "%" + text + "%", "%" + text + "%"}
+	if bounded {
+		query += " LIMIT ?"
+		args = append(args, topK*2)
+	}
+	rows, err := s.db.Query(s.q(query), args...)
 	if err != nil {
 		return nil, err
 	}