fix: [AI-190] prevent tracing exporter timeout from leaking timers

[anandgupta42]

What does this PR do?

Fixes the withTimeout helper in Tracer.endTrace() to properly clean up setTimeout timers, preventing the Node.js/Bun event loop from hanging for 5 seconds after every trace export. Also adds timeout logging for observability and aligns the HttpExporter internal timeout with the per-exporter wrapper.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Issue for this PR

Closes #190

How did you verify your code works?

• All 39 adversarial tracing tests pass (bun test test/altimate/tracing-adversarial.test.ts)
• Timeout warning log verified in test output: [tracing] Exporter "hanging" timed out after 5000ms
• TypeScript typecheck passes via turbo
• 6-model consensus code review (Claude, GPT 5.2 Codex, Gemini 3.1 Pro, Kimi K2.5, MiniMax M2.5, GLM-5) — unanimous approval

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• New and existing unit tests pass locally with my changes

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Changes:

• Add clearTimeout in .finally() to withTimeout so the event loop exits immediately after endTrace() instead of hanging for 5 seconds
• Log a console.warn when an exporter times out (uses the previously unused name parameter for diagnostics)
• Align HttpExporter internal AbortSignal.timeout from 10s to 5s to match the per-exporter wrapper timeout
• Clean up safety-net timer in adversarial test to prevent open handles

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