feat: add reasoning effort support for Codex models

- Add ReasoningEffortSelector component for UI selection
- Integrate reasoning effort in feature creation/editing dialogs
- Add reasoning effort support to phase model selector
- Update agent service and board actions to handle reasoning effort
- Add reasoning effort fields to feature and settings types
- Update model selector and agent info panel with reasoning effort display
- Enhance agent context parser for reasoning effort processing

Reasoning effort allows fine-tuned control over Codex model reasoning
capabilities, providing options from 'none' to 'xhigh' for different
task complexity requirements.

apps/ui/src/components/views/board-view/shared/model-selector.tsx

@@ -45,8 +45,8 @@ export function ModelSelector({
       // Switch to Cursor's default model (from global settings)
       onModelSelect(`${PROVIDER_PREFIXES.cursor}${cursorDefaultModel}`);
     } else if (provider === 'codex' && selectedProvider !== 'codex') {
-      // Switch to Codex's default model (gpt-5.2)
-      onModelSelect('gpt-5.2');
+      // Switch to Codex's default model (gpt-5.2-codex)
+      onModelSelect('gpt-5.2-codex');
     } else if (provider === 'claude' && selectedProvider !== 'claude') {
       // Switch to Claude's default model
       onModelSelect('sonnet');