fix(app): open new tabs in the focused pane

Preserve ambient placement for reconciliation and background opens while routing user-directed tab creation through the focused visible pane. Defer terminal reconciliation during creates so a push cannot preempt the intended pane placement.

packages/app/src/workspace-tabs/agent-visibility.test.ts

@@ -333,6 +333,7 @@ describe("workspace agent visibility", () => {
         terminalsHydrated: true,
         knownTerminalIds: ["terminal-1", "script-terminal"],
         standaloneTerminalIds: ["terminal-1"],
+        hasActivePendingTerminalCreate: false,
         hasActivePendingDraftCreate: false,
       }),
     ).toEqual({
@@ -343,6 +344,7 @@ describe("workspace agent visibility", () => {
       knownAgentIds: agentVisibility.knownAgentIds,
       knownTerminalIds: ["terminal-1", "script-terminal"],
       standaloneTerminalIds: ["terminal-1"],
+      hasActivePendingTerminalCreate: false,
       hasActivePendingDraftCreate: false,
     });
   });