0386d44fec
- Prevents absolute `AbortSignal.timeout` from cutting off active stream bodies by introducing a clearable pre-response timer. - Clears the watchdog timer for Bedrock, Gemini, Ollama, and Codex providers once headers are received. - Restores regular caller abort signaling capability on the combined fetch stream. - Adds comprehensive fake-timer tests to cover the timeout arming and clearing lifecycle.