fix: doctor --fix now repairs corrupt sessions instead of deleting them

Adds repairSessionMessages that injects synthetic tool_result messages
for orphaned tool_use blocks and drops orphaned tool_result messages.
Sessions are written back to disk with the repairs applied, preserving
conversation history.

pkg/doctor/doctor.go

@@ -294,8 +294,8 @@ func checkSessions(opts Options) Result {
 			for _, p := range problems {
 				r.AddFixable(check, SeverityError,
 					fmt.Sprintf("%s: %s", entry.Name(), p),
-					"remove corrupt session file",
+					"repair corrupt session (inject synthetic tool results, drop orphans)",
-					makeSessionDeleteFunc(filePath),
+					makeSessionRepairFunc(filePath, sess),
 				)
 			}
 		}
@@ -380,9 +380,69 @@ func checkSessionMessages(msgs []providers.Message) []string {
 	return problems
 }
 
-func makeSessionDeleteFunc(path string) func() error {
+// repairSessionMessages fixes orphaned tool_use/tool_result pairs in a message slice.
+func repairSessionMessages(msgs []providers.Message) []providers.Message {
+	if len(msgs) == 0 {
+		return msgs
+	}
+
+	// Collect all tool_call IDs
+	toolCallIDs := map[string]bool{}
+	for _, m := range msgs {
+		if m.Role == "assistant" {
+			for _, tc := range m.ToolCalls {
+				if tc.ID != "" {
+					toolCallIDs[tc.ID] = true
+				}
+			}
+		}
+	}
+
+	// Collect all tool_result IDs
+	toolResultIDs := map[string]bool{}
+	for _, m := range msgs {
+		if m.Role == "tool" && m.ToolCallID != "" {
+			toolResultIDs[m.ToolCallID] = true
+		}
+	}
+
+	// Build repaired slice: drop orphan results, inject missing results
+	repaired := make([]providers.Message, 0, len(msgs))
+	for _, m := range msgs {
+		// Drop orphaned tool_result
+		if m.Role == "tool" && m.ToolCallID != "" && !toolCallIDs[m.ToolCallID] {
+			continue
+		}
+		repaired = append(repaired, m)
+
+		// Inject missing tool_results after assistant+tool_calls
+		if m.Role == "assistant" && len(m.ToolCalls) > 0 {
+			for _, tc := range m.ToolCalls {
+				if tc.ID == "" {
+					continue
+				}
+				if !toolResultIDs[tc.ID] {
+					repaired = append(repaired, providers.Message{
+						Role:       "tool",
+						ToolCallID: tc.ID,
+						Content:    "[tool result unavailable - session was repaired by picoclaw doctor]",
+					})
+					toolResultIDs[tc.ID] = true
+				}
+			}
+		}
+	}
+	return repaired
+}
+
+func makeSessionRepairFunc(path string, sess sessionFile) func() error {
 	return func() error {
-		return os.Remove(path)
+		sess.Messages = repairSessionMessages(sess.Messages)
+		data, err := json.MarshalIndent(sess, "", "  ")
+		if err != nil {
+			return fmt.Errorf("marshaling repaired session: %w", err)
+		}
+		return os.WriteFile(path, data, 0o644)
 	}
 }
 

pkg/doctor/doctor_test.go

@@ -88,6 +88,53 @@ func TestCheckSessionMessages_ConsecutiveUserMessages(t *testing.T) {
 	}
 }
 
+func TestRepairSessionMessages_InjectsResult(t *testing.T) {
+	msgs := []providers.Message{
+		{Role: "user", Content: "hello"},
+		{
+			Role: "assistant", Content: "checking",
+			ToolCalls: []providers.ToolCall{{ID: "call_1", Name: "exec"}},
+		},
+		{Role: "assistant", Content: "done"},
+	}
+	repaired := repairSessionMessages(msgs)
+	if len(repaired) != 4 {
+		t.Fatalf("expected 4 messages, got %d", len(repaired))
+	}
+	if repaired[2].Role != "tool" || repaired[2].ToolCallID != "call_1" {
+		t.Errorf("expected injected tool_result at index 2, got role=%q id=%q",
+			repaired[2].Role, repaired[2].ToolCallID)
+	}
+}
+
+func TestRepairSessionMessages_DropsOrphanResult(t *testing.T) {
+	msgs := []providers.Message{
+		{Role: "user", Content: "hello"},
+		{Role: "tool", Content: "orphaned", ToolCallID: "call_x"},
+		{Role: "assistant", Content: "hi"},
+	}
+	repaired := repairSessionMessages(msgs)
+	if len(repaired) != 2 {
+		t.Fatalf("expected 2 messages, got %d", len(repaired))
+	}
+}
+
+func TestRepairSessionMessages_AlreadyClean(t *testing.T) {
+	msgs := []providers.Message{
+		{Role: "user", Content: "hello"},
+		{
+			Role: "assistant", Content: "checking",
+			ToolCalls: []providers.ToolCall{{ID: "call_1", Name: "exec"}},
+		},
+		{Role: "tool", Content: "output", ToolCallID: "call_1"},
+		{Role: "assistant", Content: "done"},
+	}
+	repaired := repairSessionMessages(msgs)
+	if len(repaired) != 4 {
+		t.Errorf("clean messages should be unchanged, got %d", len(repaired))
+	}
+}
+
 func TestSeverityString(t *testing.T) {
 	tests := []struct {
 		sev  Severity