[2 of 2] Finish moving goal runtime to extension (#26548)

## Stack

1. [#26547](https://github.com/openai/codex/pull/26547) - [1 of 2] Align
goal extension with core behavior
2. [#26548](https://github.com/openai/codex/pull/26548) - [2 of 2] Move
goal runtime to extension

## Why

This PR completes the switch of the goal behavior to the
extension-backed runtime and removes the old core goal implementation.

## What Changed

- Installs the goal extension for app-server `ThreadManager` sessions.
- Routes app-server thread goal `get`, `set`, and `clear` through
`GoalService`.
- Uses thread-idle lifecycle emission after goal resume and snapshot
ordering so the extension can decide whether to continue the goal.
- Forwards extension goal updates through a FIFO async app-server
notification path so backpressure does not drop them or reorder updates.
- Keeps review turns from enabling goal runtime behavior.
- Plans extension tools before dynamic tools so built-in goal tool names
keep their old precedence when goals are enabled.
- Removes the old core goal runtime, core goal tool handlers, and core
goal tool specs.
- Updates tests that were coupled to the core-owned goal runtime while
leaving the legacy `<goal_context>` compatibility path in core for old
threads.
- Removes the stale cargo-shear ignore now that `codex-goal-extension`
is used by the workspace.
- Keeps realtime event matching exhaustive after removing the old
goal-specific realtime text path.


## Validation

- Ran manual `/goal` runs in TUI. Validated time accounting matched
wall-clock time and goal lifecycle state transitions.

codex-rs/core/src/tools/spec_plan.rs

@@ -6,11 +6,9 @@ use crate::tools::context::ToolInvocation;
 use crate::tools::handlers::ApplyPatchHandler;
 use crate::tools::handlers::CodeModeExecuteHandler;
 use crate::tools::handlers::CodeModeWaitHandler;
-use crate::tools::handlers::CreateGoalHandler;
 use crate::tools::handlers::DynamicToolHandler;
 use crate::tools::handlers::ExecCommandHandler;
 use crate::tools::handlers::ExecCommandHandlerOptions;
-use crate::tools::handlers::GetGoalHandler;
 use crate::tools::handlers::ListAvailablePluginsToInstallHandler;
 use crate::tools::handlers::ListMcpResourceTemplatesHandler;
 use crate::tools::handlers::ListMcpResourcesHandler;
@@ -24,7 +22,6 @@ use crate::tools::handlers::ShellCommandHandler;
 use crate::tools::handlers::ShellCommandHandlerOptions;
 use crate::tools::handlers::TestSyncHandler;
 use crate::tools::handlers::ToolSearchHandler;
-use crate::tools::handlers::UpdateGoalHandler;
 use crate::tools::handlers::ViewImageHandler;
 use crate::tools::handlers::WriteStdinHandler;
 use crate::tools::handlers::agent_jobs::ReportAgentJobResultHandler;
@@ -305,14 +302,6 @@ fn collab_tools_enabled(turn_context: &TurnContext) -> bool {
     }
 }
 
-fn goal_tools_enabled(turn_context: &TurnContext) -> bool {
-    turn_context.goal_tools_enabled()
-        && !matches!(
-            turn_context.session_source,
-            SessionSource::SubAgent(SubAgentSource::Review)
-        )
-}
-
 fn agent_jobs_tools_enabled(turn_context: &TurnContext) -> bool {
     turn_context.features.get().enabled(Feature::SpawnCsv) && collab_tools_enabled(turn_context)
 }
@@ -558,8 +547,8 @@ fn add_tool_sources(context: &CoreToolPlanContext<'_>, planned_tools: &mut Plann
     add_core_utility_tools(context, planned_tools);
     add_collaboration_tools(context, planned_tools);
     add_mcp_runtime_tools(context, planned_tools);
-    add_dynamic_tools(context, planned_tools);
     add_extension_tools(context, planned_tools);
+    add_dynamic_tools(context, planned_tools);
     for spec in hosted_model_tool_specs(context) {
         planned_tools.add_hosted_spec(spec);
     }
@@ -639,11 +628,6 @@ fn add_core_utility_tools(context: &CoreToolPlanContext<'_>, planned_tools: &mut
     let environment_mode = turn_context.tool_environment_mode();
 
     planned_tools.add(PlanHandler);
-    if goal_tools_enabled(turn_context) {
-        planned_tools.add(GetGoalHandler);
-        planned_tools.add(CreateGoalHandler);
-        planned_tools.add(UpdateGoalHandler);
-    }
 
     if turn_context.config.experimental_request_user_input_enabled {
         planned_tools.add(RequestUserInputHandler {