agent: Add reasoning token support for OpenAI reasoning models

- Extract and display reasoning tokens from both Chat Completions and Responses APIs
- Add smart preflight detection to check reasoning support per model/API (cached per agent)
- Support both reasoning_text (o1/o3) and summary_text (gpt-5) formats
- Display reasoning tokens with ⚡ symbol in console and TUI renderers
- Only send reasoning parameters to models that support them
- Fix event type from "thinking" to "reasoning" for consistency

Note: Chat Completions API only returns reasoning token counts, not content (by design).
Only Responses API exposes actual thinking/reasoning events.

packages/agent/src/session-manager.ts

@@ -142,6 +142,7 @@ export class SessionManager implements AgentEventReceiver {
 			totalTokens: 0,
 			cacheReadTokens: 0,
 			cacheWriteTokens: 0,
+			reasoningTokens: 0,
 		};
 
 		const lines = readFileSync(this.sessionFile, "utf8").trim().split("\n");