## Why
Code Mode sessions always used client-side output handling, leaving server truncation settings and observation budgets unused.
## What changed
- Honor each session's `output_truncation` setting in the runtime and both host transports, and advertise the bounded-output capability.
- Apply `max_output_tokens` independently to execute, wait, and terminate responses in server mode. Keep client mode as the default when the setting is omitted.
- Use bounded output collection and rendering in server mode, preserving head and tail output with omission notices. Include script errors in the output budget while retaining failure status and a separate diagnostic capped at 64 KiB.
- Estimate audio tokens without the Tokio-dependent cache when rendering bounded output.
## Testing
Add runtime and host regression tests for session mode selection, per-request budgets, output overflow, oversized images, zero-token audio output, diagnostic preservation, and termination under output backpressure.
GitOrigin-RevId: 3d9661edcdd2dde31526bb92eb83fa0614f0fa88
Sean Huang
edd1ae37ec