Allow configurable continuation limits when max_iterations is reached #4560

Description

Allow configurable continuation limits when max_iterations is reached

Version: Docker Agent v1.149.0
Usage: docker agent serve api with a custom web frontend

Problem

When an agent reaches max_iterations, approving continuation always grants exactly 10 additional iterations, regardless of the configured limit.

For example, with max_iterations: 500, the agent pauses after 500 iterations. Approving continuation raises the limit to 510, then 520, and so on. This requires frequent manual confirmation during legitimate long-running tasks, such as browser automation or multi-step coding work.

The initial limit is configurable, but the continuation increment is hardcoded:

newMax := iteration + 10

Source: [pkg/runtime/loop_steps.go](https://github.com/docker/docker-agent/blob/v1.149.0/pkg/runtime/loop_steps.go#L108-L115)

The [resume API request](https://github.com/docker/docker-agent/blob/v1.149.0/pkg/api/types.go#L176-L180) exposes no parameter for changing this behavior.

Steps to reproduce

1. Configure an agent with max_iterations: 500.
2. Run a task that reaches the limit.
3. Approve continuation through the session resume API.
4. Observe that the agent can execute only 10 additional iterations before requesting confirmation again.

Proposed behavior

Allow the user to choose between:

• Continue for N additional iterations, with the original configured limit as a sensible default.
• Continue without an iteration limit for the current run.

Ideally, expose this through optional parameters on the existing resume API so custom clients can offer these choices without repeatedly auto-approving 10-iteration extensions.

These choices should affect only the current run’s iteration budget. They should not change tool approval policies, future runs, or unrelated execution limits.

For backward compatibility, requests without the new parameters could retain the existing +10 behavior.

Why this matters

An iteration limit is a useful checkpoint. Once the user explicitly approves a longer continuation, a fixed increment of 10 creates unnecessary interruptions and makes the API difficult to use for long-running workflows.

Expected Behavior

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Actual Behavior

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Steps to Reproduce

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Docker Agent version

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OS & terminal

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Model used

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Error output

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Additional context

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