Fix CLI subagent task routing, Ctrl+C cancellation, and session restore reliability

- Construct ServerTask directly for Bedrock CLI subagents so messages route
  correctly without needing a server CreateTask upgrade
- Handle CliAgentUserQuery input type in both request translators, including
  running command context and terminal output
- Add force_cancel_all_streaming_exchanges fallback for when Ctrl+C finds no
  in-flight streams (stuck subagent / unexpected stream end)
- Cancel active conversation on Ctrl+C in agent view compose state
- Skip agent view entry when agent is tagged-in for a running command
- Set root_task_id on Bedrock requests for proper optimistic task upgrade
- Persist app state on will_terminate to avoid losing sessions
- Trust persisted CWD without is_dir() recheck (fixes network mount restore)
- Log warning instead of silently dropping tabs with unreadable root nodes

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/src/ai/agent/task_store_tests.rs

@@ -44,7 +44,7 @@ fn create_test_task_with_exchanges(exchange_count: usize) -> Task {
 
 fn create_test_subtask_with_exchanges(exchange_count: usize) -> Task {
     use crate::terminal::model::block::BlockId;
-    let mut task = Task::new_optimistic_cli_agent_subtask(BlockId::new());
+    let mut task = Task::new_optimistic_cli_agent_subtask(BlockId::new(), None);
     for _ in 0..exchange_count {
         task.append_exchange(create_test_exchange());
     }
@@ -486,7 +486,7 @@ fn test_linearization_nested_subtasks() {
 
     // Create child subtask with a call to grandchild
     use crate::terminal::model::block::BlockId;
-    let mut child_subtask = Task::new_optimistic_cli_agent_subtask(BlockId::new());
+    let mut child_subtask = Task::new_optimistic_cli_agent_subtask(BlockId::new(), None);
     let child_id = child_subtask.id().clone();
 
     let child_exchange1 = create_test_exchange();