Add goal app-server API (2 / 5) (#18074)

Adds the app-server v2 goal API on top of the persisted goal state from
PR 1.

## Why

Clients need a stable app-server surface for reading and controlling
materialized thread goals before the model tools and TUI can use them.
Goal changes also need to be observable by app-server clients, including
clients that resume an existing thread.

## What changed

- Added v2 `thread/goal/get`, `thread/goal/set`, and `thread/goal/clear`
RPCs for materialized threads.
- Added `thread/goal/updated` and `thread/goal/cleared` notifications so
clients can keep local goal state in sync.
- Added resume/snapshot wiring so reconnecting clients see the current
goal state for a thread.
- Added app-server handlers that reconcile persisted rollout state
before direct goal mutations.
- Updated the app-server README plus generated JSON and TypeScript
schema fixtures for the new API surface.

## Verification

- Added app-server v2 coverage for goal get/set/clear behavior,
notification emission, resume snapshots, and non-local thread-store
interactions.

codex-rs/tui/src/app/app_server_adapter.rs

@@ -350,6 +350,12 @@ fn server_notification_thread_target(
         ServerNotification::ThreadTokenUsageUpdated(notification) => {
             Some(notification.thread_id.as_str())
         }
+        ServerNotification::ThreadGoalUpdated(notification) => {
+            Some(notification.thread_id.as_str())
+        }
+        ServerNotification::ThreadGoalCleared(notification) => {
+            Some(notification.thread_id.as_str())
+        }
         ServerNotification::TurnStarted(notification) => Some(notification.thread_id.as_str()),
         ServerNotification::HookStarted(notification) => Some(notification.thread_id.as_str()),
         ServerNotification::TurnCompleted(notification) => Some(notification.thread_id.as_str()),

codex-rs/tui/src/chatwidget.rs

@@ -6533,6 +6533,8 @@ impl ChatWidget {
                     notification.token_usage,
                 )));
             }
+            ServerNotification::ThreadGoalUpdated(_) => {}
+            ServerNotification::ThreadGoalCleared(_) => {}
             ServerNotification::ThreadNameUpdated(notification) => {
                 match ThreadId::from_string(&notification.thread_id) {
                     Ok(thread_id) => self.on_thread_name_updated(
@@ -7089,6 +7091,7 @@ impl ChatWidget {
         match msg {
             EventMsg::SessionConfigured(e) => self.on_session_configured(e),
             EventMsg::ThreadNameUpdated(e) => self.on_thread_name_updated(e),
+            EventMsg::ThreadGoalUpdated(_) => {}
             // NOTE: All three AgentMessage arms feed `record_agent_markdown` even
             // when the message is otherwise not rendered (thread-snapshot replay,
             // non-review live messages). This ensures the copy source stays
@@ -7200,6 +7203,9 @@ impl ChatWidget {
                 TurnAbortReason::ReviewEnded => {
                     self.on_interrupted_turn(ev.reason);
                 }
+                TurnAbortReason::BudgetLimited => {
+                    self.on_interrupted_turn(ev.reason);
+                }
             },
             EventMsg::PlanUpdate(update) => self.on_plan_update(update),
             EventMsg::ExecApprovalRequest(ev) => {