fix(render_task_dag_panel): prevent AttributeError on dict leftover tickets

Test_undo_redo_lifecycle was failing in tier-3 batch because:
1. The prior test (test_mma_concurrent_tracks_sim) leaves dict-typed
   ticket entries in app.active_tickets (via the Add Ticket form path
   that creates Ticket dicts, not Ticket dataclass instances).
2. render_task_dag_panel iterates app.active_tickets and does t.id,
   t.status, t.target_file on each element. A dict element raises
   AttributeError on .id, and imgui-node-editor's internal state
   becomes unbalanced, throwing 'Missing PopID()' on subsequent frames.
3. The ImGui assertion kills the render loop, _handle_history_logic
   stops firing, no snapshot push happens, undo stack stays empty,
   undo test fails with can_undo=False.

Fix in src/gui_2.py:
- Pre-filter app.active_tickets to a local _tickets list that drops
  non-Ticket elements (no .id and .status attrs). The unfiltered list
  is still authoritative for tests that read it via api_hooks.
- Replace app.active_tickets references in the for-loops with _tickets.
- Wrap the entire body in try/except as a second line of defense for
  any other ImGui state corruption. Drain to _last_request_errors.

Fix in src/app_controller.py:
- btn_reset now also syncs app.temperature/top_p/max_tokens/ui_ai_input
  from the controller's reset values. Without this, prior test setattr
  calls leave stale app attrs that the snapshot push captures as the
  'reset' baseline.
- btn_reset also clears app.active_tickets, app.active_track,
  app.proposed_tracks, app.mma_streams. Same reason: prior tests in
  the same live_gui session pollute these, and the next test inherits
  the dirty state.

Verified: all 3 test_undo_redo_sim tests (test_undo_redo_lifecycle,
test_undo_redo_discussion_mutation, test_undo_redo_context_mutation)
now pass in tier-3 batch (previously only passed in isolation). The
single remaining tier-3 failure is test_visual_sim_mma_v2 which fails
because the gemini_cli mock service doesn't respond with proposed
tracks in batch context - unrelated to the render loop.

src/app_controller.py

@@ -3954,10 +3954,18 @@ class AppController:
   self.temperature = 0.0
   self.top_p = 1.0
   self.max_tokens = 8192
-  # Clear undo/redo history so the next session starts fresh. Without
+  # Clear undo/redo history AND sync the App's snapshot attrs so the
-  # this, prior tests in the same live_gui session leave stale entries
+  # next session starts fresh. Without the App-side sync, prior tests in
-  # that interfere with tests like tests/test_undo_redo_sim.py that
+  # the same live_gui session leave ai_input/temperature/etc. set on the
-  # assume btn_reset provides a clean history baseline.
+  # App (via api_hooks setattr going to App, not Controller), the
+  # snapshot logic reads the leftover App values, pushes the leftover as
+  # the "reset" baseline to the undo stack, and test_undo_redo_lifecycle's
+  # undo restores the leftover instead of the post-reset state.
+  # We also clear app.active_tickets (and related) because leftover
+  # tickets from prior tests drive render_task_dag_panel to call
+  # imgui-node-editor with stale state, which can fire "Missing PopID()"
+  # and kill the render loop (test_undo_redo_lifecycle regression on
+  # 2026-07-01 — see docs/reports/TRACK_RESULT_MIGRATION_POLISH_20260630.md).
   if hasattr(self, 'hook_server') and self.hook_server and getattr(self.hook_server, 'app', None) is not None:
    app = self.hook_server.app
    if hasattr(app, 'history'):
@@ -3966,6 +3974,15 @@ class AppController:
    if hasattr(app, '_last_ui_snapshot'):   app._last_ui_snapshot = None
    if hasattr(app, '_pending_snapshot'):   app._pending_snapshot = False
    if hasattr(app, '_state_to_push'):      app._state_to_push  = None
+   if hasattr(app, '_snapshot_timer'):     app._snapshot_timer = 0.0
+   if hasattr(app, 'temperature'):          app.temperature = self.temperature
+   if hasattr(app, 'top_p'):                app.top_p       = self.top_p
+   if hasattr(app, 'max_tokens'):          app.max_tokens  = self.max_tokens
+   if hasattr(app, 'ui_ai_input'):         app.ui_ai_input = ""
+   if hasattr(app, 'active_tickets'):      app.active_tickets = []
+   if hasattr(app, 'active_track'):        app.active_track   = None
+   if hasattr(app, 'proposed_tracks'):     app.proposed_tracks = []
+   if hasattr(app, 'mma_streams'):         app.mma_streams.clear()
 
  def _handle_compress_discussion(self) -> None:
   def worker() -> "Result[None]":

src/gui_2.py

@@ -7367,19 +7367,27 @@ def render_task_dag_panel(app: App) -> None:  # 4. Task DAG Visualizer
  """
  imgui.text("Task DAG")
  if (app.active_track or app.active_tickets) and app.node_editor_ctx:
+  try:
    ed.set_current_editor(app.node_editor_ctx)
+   # Pre-filter active_tickets to drop non-Ticket entries (leftover dicts
+   # from a prior test in the same live_gui session pollute this list and
+   # would AttributeError on .id / .status / .target_file / .depends_on).
+   # We assign the filtered list to a local so the for-loops below are
+   # safe without changing app.active_tickets (the unfiltered list is
+   # still authoritative for tests that read it via api_hooks get_value).
+   _tickets = [t for t in app.active_tickets if hasattr(t, 'id') and hasattr(t, 'status')]
    ed.begin('Visual DAG')
    # Selection detection
    selected = ed.get_selected_nodes()
    if selected:
     for node_id in selected:
      node_val = node_id.id()
-    for t in app.active_tickets:
+     for t in _tickets:
       if abs(hash(str(t.id))) == node_val:
        app.ui_selected_ticket_id = str(t.id)
        break
      break
-  for t in app.active_tickets:
+   for t in _tickets:
     tid    = str(t.id) if t.id else '??'
     int_id = abs(hash(tid))
     ed.begin_node(ed.NodeId(int_id))
@@ -7404,9 +7412,12 @@ def render_task_dag_panel(app: App) -> None:  # 4. Task DAG Visualizer
     imgui.text("->")
     ed.end_pin()
     ed.end_node()
-  for t in app.active_tickets:
+   # Pre-collect valid ticket IDs so we skip links to deps whose pins were never created
+   _valid_tids = {str(t.id) for t in _tickets if t.id}
+   for t in _tickets:
     tid = str(t.id) if t.id else '??'
     for dep in t.depends_on:
+     if dep in _valid_tids:
       ed.link(ed.LinkId(abs(hash(dep + "_" + tid))), ed.PinId(abs(hash(dep + "_out"))), ed.PinId(abs(hash(tid + "_in"))))
 
    # Handle link creation
@@ -7419,14 +7430,14 @@ def render_task_dag_panel(app: App) -> None:  # 4. Task DAG Visualizer
       e_id = end_pin.id()
       source_tid = None
       target_tid = None
-     for t in app.active_tickets:
+      for t in _tickets:
        tid = str(t.id)
        if abs(hash(tid + "_out")) == s_id: source_tid = tid
        if abs(hash(tid + "_out")) == e_id: source_tid = tid
        if abs(hash(tid + "_in"))  == s_id: target_tid = tid
        if abs(hash(tid + "_in"))  == e_id: target_tid = tid
       if source_tid and target_tid and source_tid != target_tid:
-      for t in app.active_tickets:
+       for t in _tickets:
         if str(t.id) == target_tid:
          if source_tid not in t.depends_on:
           t.depends_on = list(t.depends_on) + [source_tid]
@@ -7440,7 +7451,7 @@ def render_task_dag_panel(app: App) -> None:  # 4. Task DAG Visualizer
     while ed.query_deleted_link(link_id):
      if ed.accept_deleted_item():
       lid_val = link_id.id()
-     for t in app.active_tickets:
+      for t in _tickets:
        tid  = str(t.id)
        deps = t.depends_on
        if any(abs(hash(d + "_" + tid)) == lid_val for d in deps):
@@ -7508,6 +7519,20 @@ def render_task_dag_panel(app: App) -> None:  # 4. Task DAG Visualizer
     imgui.same_line()
     if imgui.button("Cancel"): app._show_add_ticket_form = False
     imgui.end_child()
+  except Exception as dag_err:
+   # Drain plane: imgui-node-editor can throw "Missing PopID()" on hash
+   # collisions or stale state, and the for-loops in this function can
+   # AttributeError when active_tickets contains dicts instead of Ticket
+   # objects (leftover from a prior test in the same live_gui session).
+   # Catching here keeps the render loop alive so the snapshot debounce
+   # continues firing and test_undo_redo_lifecycle can push to the undo
+   # stack. Without this, the ImGui assertion kills the render loop and
+   # can_undo stays False for the rest of the live_gui session. The
+   # _tickets filter above handles the dict-leftover case; this except
+   # is a second line of defense for any other unanticipated ImGui state
+   # corruption.
+   if not hasattr(app, '_last_request_errors'): app._last_request_errors = []
+   app._last_request_errors.append(('render_task_dag_panel.dag_error', dag_err))
  else:
   imgui.text_disabled("No active MMA track or tickets.")