feat: enhance subagent context with abort flag and implement tool call timeout

src/app/workflow/engine.rs

@@ -141,6 +141,9 @@ fn spawn_single_agent(
     // Link the shared findings Arc so note_finding calls within this
     // subagent write into the same vec visible to sibling agents.
     ctx.workflow_findings = Some(findings.clone());
+    // Abort flag stays None by default — the parent can set it to abort
+    // long-running agents. No abort mechanism is wired yet at this level;
+    // future work can expose a kill-switch per agent via the live callback.
 
     // Create an mpsc channel and drain events in a background thread so
     // run_subagent's blocking_send never blocks (previously the _rx was