[codex] add current time reminder delivery mode config (#30031)

```python
delivery_mode = "any_inference" # default
delivery_mode = "after_user_or_tool_output" # new mode
``` 

## Validation
- just test -p codex-core load_config_resolves_current_time_reminder
- just test -p codex-core
lock_contains_prompts_and_materializes_features

codex-rs/core/src/config/config_tests.rs

@@ -627,11 +627,13 @@ current_time_reminder = true
 enabled = true
 reminder_interval_seconds = 0
 clock_source = "external"
+delivery_mode = "after_user_or_tool_output"
 sleep_tool = true
 "#,
             CurrentTimeReminderConfig {
                 reminder_interval_seconds: 0,
                 clock_source: CurrentTimeSource::External,
+                delivery_mode: CurrentTimeReminderDeliveryMode::AfterUserOrToolOutput,
                 sleep_tool: true,
             },
         ),

codex-rs/core/src/config/mod.rs

@@ -59,6 +59,7 @@ use codex_exec_server::ExecutorFileSystem;
 use codex_exec_server::LOCAL_FS;
 use codex_features::CodeModeConfigToml;
 use codex_features::CurrentTimeReminderConfigToml;
+use codex_features::CurrentTimeReminderDeliveryMode;
 use codex_features::CurrentTimeSource;
 use codex_features::Feature;
 use codex_features::FeatureConfigSource;
@@ -1120,6 +1121,7 @@ pub struct RolloutBudgetConfig {
 pub struct CurrentTimeReminderConfig {
     pub reminder_interval_seconds: u64,
     pub clock_source: CurrentTimeSource,
+    pub delivery_mode: CurrentTimeReminderDeliveryMode,
     /// Whether to expose the input-interruptible `clock.sleep` tool.
     pub sleep_tool: bool,
 }
@@ -1129,6 +1131,7 @@ impl Default for CurrentTimeReminderConfig {
         Self {
             reminder_interval_seconds: 1,
             clock_source: CurrentTimeSource::System,
+            delivery_mode: CurrentTimeReminderDeliveryMode::AnyInference,
             sleep_tool: false,
         }
     }
@@ -2691,6 +2694,9 @@ fn resolve_current_time_reminder_config(
         clock_source: base
             .and_then(|config| config.clock_source)
             .unwrap_or(default.clock_source),
+        delivery_mode: base
+            .and_then(|config| config.delivery_mode)
+            .unwrap_or(default.delivery_mode),
         sleep_tool: base
             .and_then(|config| config.sleep_tool)
             .unwrap_or(default.sleep_tool),

codex-rs/core/src/session/config_lock.rs

@@ -361,6 +361,7 @@ mod tests {
                 enabled: Some(true),
                 reminder_interval_seconds: Some(1),
                 clock_source: Some(codex_features::CurrentTimeSource::System),
+                delivery_mode: Some(codex_features::CurrentTimeReminderDeliveryMode::AnyInference),
                 sleep_tool: Some(false),
             }))
         );