feat: resolve old inline comments when superseding review

Closes #27

After superseding an old review, resolves all its inline comments via
POST /pulls/comments/{id}/resolve. This clears unresolved conversation
markers from the PR timeline and diff view.

New API methods:
- ListReviewComments: paginated GET /repos/.../pulls/{n}/reviews/{id}/comments
- ResolveComment: POST /repos/.../pulls/comments/{id}/resolve

Behavior:
- Only resolves after successful supersede (gated on supersedeOK)
- Aggregates failures and logs at warn level
- Truncates error bodies to 256 bytes (security)
- Non-fatal: review still posts even if resolution fails

gitea/client_test.go

@@ -684,3 +684,62 @@ func TestRequestReviewer_Error(t *testing.T) {
 		t.Errorf("error should mention status code: %v", err)
 	}
 }
+
+func TestListReviewComments(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if !strings.Contains(r.URL.Path, "/pulls/1/reviews/42/comments") {
+			t.Errorf("unexpected path: %s", r.URL.Path)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprint(w, `[{"id":100,"path":"main.go","new_position":5,"body":"finding"},{"id":101,"path":"lib.go","new_position":10,"body":"another"}]`)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "test-token")
+	comments, err := client.ListReviewComments(context.Background(), "owner", "repo", 1, 42)
+	if err != nil {
+		t.Fatalf("ListReviewComments() error = %v", err)
+	}
+	if len(comments) != 2 {
+		t.Fatalf("got %d comments, want 2", len(comments))
+	}
+	if comments[0].ID != 100 {
+		t.Errorf("comments[0].ID = %d, want 100", comments[0].ID)
+	}
+	if comments[1].Path != "lib.go" {
+		t.Errorf("comments[1].Path = %q, want %q", comments[1].Path, "lib.go")
+	}
+}
+
+func TestResolveComment(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			t.Errorf("expected POST, got %s", r.Method)
+		}
+		if !strings.Contains(r.URL.Path, "/pulls/comments/99/resolve") {
+			t.Errorf("unexpected path: %s", r.URL.Path)
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "test-token")
+	err := client.ResolveComment(context.Background(), "owner", "repo", 99)
+	if err != nil {
+		t.Fatalf("ResolveComment() error = %v", err)
+	}
+}
+
+func TestResolveComment_Error(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+		fmt.Fprint(w, "not found")
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "test-token")
+	err := client.ResolveComment(context.Background(), "owner", "repo", 99)
+	if err == nil {
+		t.Fatal("expected error for 404 response")
+	}
+}