fix(search): emit pagination cursor on first truncated page

On the first page (offset==0) ripgrep capped results at exactly max_results
and set Truncated=true, but the cursor-footer guard (len>max_results) was
false, so the response said "(truncated...)" with no cursor — the caller
was told more matches exist but given no way to fetch them. Pagination only
worked from page 2. Emit a cursor on the first page using rg's total match
count for the remaining estimate.

Adds a strict regression test (asserts, not skips); the existing pagination
test was silently skipping its round-trip because page 1 never had a cursor.

internal/server/features_test.go

@@ -292,6 +292,39 @@ func TestFileSearchCursorStaleHash(t *testing.T) {
 	}
 }
 
+// TestFileSearchFirstPageCursor is a strict regression guard: when the first
+// page is capped by max_results but more matches exist, the response MUST carry
+// a cursor so the caller can page. Previously offset==0 emitted "(truncated...)"
+// with no cursor, silently breaking pagination on the common path.
+func TestFileSearchFirstPageCursor(t *testing.T) {
+	srv, tmpDir := newFeaturesServer(t)
+	if srv.searcher == nil {
+		t.Skip("rg not available")
+	}
+	ctx := context.Background()
+
+	// Corpus has 5 lines containing "func"; cap at 1 forces truncation on page 1.
+	req := mcp.CallToolRequest{}
+	req.Params.Arguments = map[string]interface{}{
+		"pattern":       "func",
+		"paths":         []interface{}{tmpDir},
+		"max_results":   float64(1),
+		"context_lines": float64(0),
+	}
+	res, err := srv.handleFileSearch(ctx, req)
+	if err != nil {
+		t.Fatalf("file_search error: %v", err)
+	}
+	text := res.Content[0].(mcp.TextContent).Text
+	if !strings.Contains(text, "[cursor:") {
+		t.Errorf("first page truncated at max_results=1 with 5 matches must emit a cursor, got:\n%s", text)
+	}
+	// The dead-end prose must not be used when a cursor is available.
+	if strings.Contains(text, "(truncated, showing subset") {
+		t.Errorf("dead-end truncation prose should be replaced by a cursor footer, got:\n%s", text)
+	}
+}
+
 func TestFileSearchPaginationCursor(t *testing.T) {
 	srv, tmpDir := newFeaturesServer(t)
 	if srv.searcher == nil {

internal/server/handlers_file.go

@@ -127,13 +127,23 @@ func (s *Server) handleFileSearch(ctx context.Context, request mcp.CallToolReque
 
 	// Apply in-process max_results cap and compute cursor footer.
 	var cursorLine string
-	if maxResults > 0 && len(results.Results) > maxResults {
+	switch {
+	case maxResults > 0 && len(results.Results) > maxResults:
+		// Cursor pages (offset>0) fetch all results, so cap here and emit a cursor.
 		remaining := len(results.Results) - maxResults
 		results.Results = results.Results[:maxResults]
 		results.Truncated = true
 		nextOffset := offset + maxResults
 		nextCursor := cursor.Encode(nextOffset, queryHash)
 		cursorLine = fmt.Sprintf("[cursor: %s, remaining: %d]", nextCursor, remaining)
+	case offset == 0 && maxResults > 0 && results.Truncated:
+		// First page: ripgrep capped us at exactly maxResults in parseOutput, but
+		// more matches exist. Emit a cursor so the caller can page instead of being
+		// told "truncated" with no way to continue. remaining derives from rg's
+		// total match count (a submatch count — an upper-bound proxy for rows).
+		nextCursor := cursor.Encode(maxResults, queryHash)
+		remaining := max(results.Total-maxResults, 1)
+		cursorLine = fmt.Sprintf("[cursor: %s, remaining: %d]", nextCursor, remaining)
 	}
 
 	s.logger.Info("search completed",